This is a regular verb with a spelling change. It follows the conjugation pattern of the verb hablar.
Spelling Change: ge gue - gé gué
PresentPresente
El niño pega fotos en su cuaderno.
The boy sticks photos in his notebook.
PreteritePretérito indefinido
Pegué el cartel en la pared.
I stuck the poster on the wall.
Negative ImperativeImperativo negativo
No le pegues a tu hermana.
Don't hit your sister.