To say ‘I am full’ in Spanish, you would say ‘Estoy lleno’ if you are male, or ‘Estoy llena’ if you are female.
This phrase is commonly used after a meal when you want to express that you have eaten enough and cannot eat more. The verb ‘estar’ is used here because it describes a temporary state, which in this case is the feeling of being full. The word ‘lleno/a’ means ‘full’ and must agree in gender with the speaker.