Setting An Entities Parent

How do I make one entity set its parent to another causing it to move the other when I move it’s parent?
I’ve already tried this many times with the self:SetParent() but it won’t work, I don’t know what else to do.
This would be like if I touched an entity on to another entity, how would I make that entity set it’s parent to the one it just touched.

SetParent must have the movetype set to Entity:SetMoveType( MOVETYPE_NONE ), so maybe that’s why SetParent wasn’t working? Also, you need to specify which entity to parent your entity to. You also need to specify the attachment id