The obligatory recitation in Tashahhud in Salah is : ASHHADU ANLA ELAAHA ELLALLAH WAHDAHU LA SHAREEKA LAH WA ASHHADU ANNA MUHAMMADAN ABDOHU WA RASOOLOH ALLAHUMMA SALLI ALA MUHAMMADIN WA AALI MOHAMMAD.
There are recommended recitations before and after Tashahhud which can be found in many books and it can be short or long depending on what you want to recite.
Wassalam.