Let H be a subgroup of G and let a be in G. Show that aHa^-1 is a subgroup of G that is isomorphic to H.

I want to show aHa^-1 is 1-1, onto and has a homomorphism property.

Ok so my problem with this is that with isomorphisms before I generally had a function that I worked from, so it was easier to show 1-1, onto, and c(ab)=c(a)c(b), but without a funcction, I get stuck beginning.