I believe you may get some tips from the answers to a question of mine on this very site: “Do you list journals you have reviewed for on your CV?”
As for myself, I list the peer-reviews I have done in a “Administrative and collective duties” or “Community involvement”. Or, in a short CV which doesn't have such divisions, I put it with the broader “Other skills and activities” section (i.e. not teaching, not research projects).
What I include is:
- list of journals for which I act as reviewer (“Regular reviewer for many chemistry journals, including …”)
- funding bodies (NSF, private trusts, etc.) for which I act as expert (including, e.g., NSF division, but not the exact programs)
- evaluation committees on which I sit
It feels obvious, but it's always worth repeating: do not include any confidential information, such as titles or author lists for reviewer papers or projects. I think it's safe to list the number of reviews performed for each outlet if you want (but I don't do it).