Al salam alaykom! Welcome to the New Muslim Workshop. Today we are teaching New Muslims (#Reverts) how say Al-Tahiyat which is also know as Al Tashahud Al Awal (The First Tashahud). The is said at the end of some prayers and the Middle and end of others.
For The Dawn Prayers (Fajr) it happens only at the end of the 2nd Rak'a
For the Noon Prayers (Thuhr) it happens at th the end of the 2nd and 4th Rak'as
For the Afternoon Prayers (Asr) it happens at the end of the 2nd and 4th Rak'as
For the Maghrib Prayers (Sunset) it happens at the end of the 2nd and 3rd Rak'as
For the Isha Prayer (Night) it happens at the end of the 2nd and 4th Rak'as.

The Transliteration of Al-Tahiyat is:
Al-Tahiyato Lilahu Wal Salawaato Waltayibaat
Al Salamo Alayka Auhal Nabi Wa Rahmatu Allahi Wa Barkaato
Al Salamo Alayna wa Ala ibaad Allah al Saliheen
Ash-hadu An La ilaha ila Allah
Wa Ash-hadu Ana Muhammadan Abduhu wa Rasooloh

The source of this in the Sunnah is:

أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا عَبْثَرٌ، عَنِ الأَعْمَشِ، عَنْ أَبِي إِسْحَاقَ، عَنْ أَبِي الأَحْوَصِ، عَنْ عَبْدِ اللَّهِ، قَالَ عَلَّمَنَا رَسُولُ اللَّهِ صلى الله عليه وسلم التَّشَهُّدَ فِي الصَّلاَةِ وَالتَّشَهُّدَ فِي الْحَاجَةِ فَأَمَّا التَّشَهُّدُ فِي الصَّلاَةِ ‏ "‏ التَّحِيَّاتُ لِلَّهِ وَالصَّلَوَاتُ وَالطَّيِّبَاتُ السَّلاَمُ عَلَيْكَ أَيُّهَا النَّبِيُّ وَرَحْمَةُ اللَّهِ وَبَرَكَاتُهُ السَّلاَمُ عَلَيْنَا وَعَلَى عِبَادِ اللَّهِ الصَّالِحِينَ أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَأَشْهَدُ أَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ ‏"‏ ‏.‏ إِلَى آخِرِ التَّشَهُّدِ ‏.‏

It was narrated that 'Abdullah said: "The Messenger of Allah (ﷺ) taught us the tashahhud for prayer and the tashahhud for Al-Hajah. The tashahhud for prayer is: At-tahiyyatu lillahi was-salawatu wat-tayyibat, as-salamu 'alaika ayyuhan-Nabiyyu wa rahmatAllahi wa baraktuhu. As-salamu 'alaina wa 'ala 'ibad illahis-salihin, ashahdu an la illaha ill-Allah wa ashhadu anna Muhammadan 'abduhu wa rasuluhu (Allah compliments, prayers and pure words are due to Allah. Peace be upon you, O Prophet, and the mercy of Allah (SWT) and his blessings. Peace be upon us and upon the righteous slaves of Allah (SWT). I bear witness that none has the right to be worshipped except Allah and I bear witness that Muhammad is His slave and Messenger).' (to the end of the tashahhud)"

Sunan an-Nasa'i 1164
Grade: Sahih (Darussalam)
https://sunnah.com/nasai:1164