The first thing to do after entering Makkah is to perform Umrah, but how is Umrah performed?

Upon entering Al-Masjid al-Haram, first perform seven circuits of tawaf around the Ka'bah. Then, after offering two rak'ahs of prayer, perform sa'i seven times between the hills of Safa and Marwah. Finally, cut your hair and come out of ihram; that is, change out of the ihram garments and put on normal clothing. See the following chapters for the detailed rules of tawaf, sa'i, and cutting the hair.