It is highly advisable to engage yourself in  glorification of Almighty Allah and implorations for His forgiveness, because this hour is as important  as the pre-sunrise hour, as Almighty Allah has said in the Holy Quran:
وَسَبِّحْ بِحَمْدِ رَبِّكَ قَبْلَ طُلُوعِ ٱلشَّمْسِ وَقَبْلَ ٱلْغُرُوبِ.
And sing the praise of your Lord before the rising of the sun and before the setting.

Imam al-Sadiq (`a) is reported to have said, “When the color of the sun changes (i.e. the sun is about to set), you must remember Allah the Almighty and Majestic. If you are at that hour with one who preoccupies you from this, you must leave him and supplicate.

امْسَىٰ ظُلْمِي مُسْتَجِيراً بِعَفْوِكَ
amsa zulmi mustajiran bi`afwika
In this evening, my wrongdoing is taking shelter in Your pardon,
وَامْسَتْ ذُنُوبِي مُسْتَجِيرَةً بِمَغْفِرَتِكَ
wa amsat dhunubi mustajiratan bimaghfiratika
my sins are taking shelter in Your forgiveness,
وَامْسىٰ خَوْفِي مُسْتَجِيراً بِامَانِكَ
wa amsa khawfi mustajiran bi’amanika
my fear is taking shelter in Your security,
وَامْسَىٰ ذُلِّي مُسْتَجِيراً بِعِزِّكَ
wa amsa dhulli mustajiran bi`izzika
my humility is taking shelter in Your dignity,
وَامْسَىٰ فَقْرِي مُسْتَجِيراً بِغِنَاكَ
wa amsa faqri mustajiran bighinaka
my poverty is taking shelter in Your richness,
وَامْسَىٰ وَجْهِيَ ٱلْبَالِي مُسْتَجِيراً بِوَجْهِكَ ٱلدَّائِمِ ٱلْبَاقِي
wa amsa wajhiya albali mustajiran biwajhika aldda’imi albaqi
and my mortal face is taking shelter in Your Face, the Undying and Perpetual.
اللَّهُمَّ الْبِسْنِي عَافِيَتَكَ
allahumma albisni `afiyataka
O Allah, (please) dress me with Your wellbeing,
وَغَشِّنِي بِرَحْمَتِكَ
wa ghashshini birahmatika
cover me with Your mercy,
وَجَلِّلْنِي كَرَامَتَكَ
wa jallilni karamataka
overshadow me with Your honoring,
وَقِنِي شَرَّ خَلْقِكَ مِنَ ٱلْجِنِّ وَٱلإِنْسِ
wa qini sharra khalqika min aljinni wal-insi
and protect me against the evils of Your creatures—jinn and men.
يَا اللَّهُ يَا رَحْمٰنُ يَا رَحِيمُ
ya allahu ya rahmanu ya rahimu
O Allah! O All-beneficent! O All-merciful!

Continue the supplication to be said at sunset as under:

يَا مَنْ خَتَمَ ٱلنُّبُوَّةَ بِمُحَمَّدٍ
ya man khatama alnnubuwwata bimuhammadin
O He Who has sealed the Prophethood with Muhammad,

صَلَّىٰ ٱللَّهُ عَلَيْهِ وَآلِهِ
salla allahu `alayhi wa alihi
Allah may bless him and his Household,
إِخْتِمْ لِي فِي يَوْمِي هٰذَا بِخَيْرٍ
ikhtim li fi yawmi hadha bikhayrin
(please) seal with goodness this day of mine,
وَشَهْرِي بِخَيْرٍ
wa shahri bikhayrin
this month of mine,
وَسَنَتِي بِخَيْرٍ
wa sanati bikhayrin
this year of mine,
وَعُمْرِي بِخَيْرٍ
wa `umri bikhayrin
and my entire lifetime.

You may say the words of professing that there is no god save Allah and the words of seeking His protection, . You may then put your hand on the head and pass it over your face.

You may then hold your beard and say the following

حَطْتُ عَلَىٰ نَفْسِي وَاهْلِي
ahattu `ala nafsi wa ahli
I include myself, my family,
وَمَالِي وَوَلَدِي
wa mali wa waladi
my property, and my sons,
مِنْ غَائِبٍ وَشَاهِدٍ
min gha’ibin wa shahidin
both the absent and the present
بِٱللَّهِ ٱلَّذِي لاَ إِلٰهَ إِلاََّ هُوَ
billahi alladhi la ilaha illa huwa
with Allah save Whom there is no god,
عَالِمُ ٱلْغَيْبِ وَٱلشَّهَادَةِ
`alimu alghaybi walshshahadati
the Knower of the unseen and the seen,
ٱلرَّحْمٰنُ ٱلرَّحِيمُ
alrrahmanu alrrahimu
the All-beneficent, the All-merciful,
ٱلْحَيُّ ٱلْقَيُّومُ
alhayyu alqayyumu
the Ever-living, the Self-subsisting.
لاَ تَاخُذُهُ سِنَةٌ وَلاَ نَوْمٌ
la ta’khudhuhu sinatun wa la nawmun
Slumber does not overtake Him nor sleep.
لَهُ مَا فِي ٱلسَّمَاوَاتِ وَمَا فِي ٱلارْضِ
lahu ma fi alssamawati wa ma fi al-ardi
Whatever is in the heavens and whatever is in the earth is His.
مَنْ ذَا ٱلَّذِي يَشْفَعُ عِنْدَهُ إِلاَّ بِإِذْنِهِ
man dha alladhi yashfa`u `indahu illa bi’idhnihi
Who is he that can intercede with Him but by His permission?
يَعْلَمُ مَا بَيْنَ ايْدِيهِمْ وَمَا خَلْفَهُمْ
ya`lamu ma bayna aydihim wa ma khalfahum
He knows what is before them and what is behind them,
وَلا يُحِيطُونَ بِشَيْءٍ مِنْ عِلْمِهِ إِلاَّ بِمَا شَاءَ
wa la yuhituna bishay’in min `ilmihi illa bima sha’a
and they cannot comprehend anything out of His knowledge except what He pleases.
وَسِعَ كُرْسِيُّهُ ٱلسَّمَاوَاتِ وَٱلارْضَ
wasi`a kursiyyuhu alssamawati wa al-arda
His knowledge extends over the heavens and the earth,
وَلاَ يَئُودُهُ حِفْظُهُمَا
wa la ya’uduhu hifzuhuma
and the preservation of them both tires Him not,
وَهُوَ ٱلْعَلِيُّ ٱلْعَظِيمُ
wa huwa al`aliyyu al`azimu
and He is the Most High, the Great.