For Salat al-Istikhara, perform Wudu before starting the Istikhara Nafl. You can perform Salat al-Istikhara at any time, except during the prohibited times for prayers that are Fajr until sunrise or after Asr until sunset. However, the most recommended time is after Isha Namaz. After Isha Namaz, perform two Nafl with the intention of Istikhara. Upon completing the Salat al-Istikhara, recite the following dua.

اللَّهُمَّ إِنِّي أَسْتَخِيرُكَ بِعِلْمِكَ وَأَسْتَقْدِرُكَ بِقُدْرَتِكَ وَأَسْأَلُكَ مِنْ فَضْلِكَ الْعَظِيمِ فَإِنَّكَ تَقْدِرُ وَلَا أَقْدِرُ وَتَعْلَمُ وَلَا أَعْلَمُ وَأَنْتَ عَلَّامُ الْغُيُوبِ اللَّهُمَّ إِنْ كُنْتَ تَعْلَمُ أَنَّ هَذَا الْأَمْرَ خَيْرٌ لِي فِي دِينِي وَمَعَاشِي وَعَاقِبَةِ أَمْرِي فَاقْدُرْهُ لِي وَيَسِّرْهُ لِي ثُمَّ بَارِكْ لِي فِيهِ وَإِنْ كُنْتَ تَعْلَمُ أَنَّ هَذَا الْأَمْرَ شَرٌّ فِي دِينِي وَمَعَاشِي وَعَاقِبَةِ أَمْرِي فَاصْرِفْهُ عَنِّي وَاصْرِفْنِي عَنْهُ وَاقْدُرْ لِيَ الْخَيْرَ حَيْثُ كَانَ ثُمَّ ارْضِنِي بِهِ

Allahumma innee astakheeruka bi ‘ilmika wa astaqdiruka bi qadratika wa as’aluka min fadlika al-’adheem fa innaka taqdiru wa la aqdiru wa ta’lamu wa la a’lamu wa anta ‘allaam ul-ghuyoob. Allahumma in kunta ta’lamu anna haadha al-amra khayrun lee fee deenee wa ma’aashee wa ‘aaqibati amree faqdurhu lee wa yassirhu lee thumma baarik lee feehi wa in kunta ta’lamu anna haadha al-amara sharrun lee fee deenee wa ma’aashee wa ‘aaqibati amree fasrifhu ‘annee wasrifnee ‘anhu waqdur lee al-khayra haythu kaana thumma ardinee bih