Most beta tests for software have a non-disclosure agreement which often prohibits even stating one was part of any beta testing. If your agreements permit disclosure of the testing, then merely listing the software titles under beta testing would be sufficient.

I don't really know how much of a favorable impression it will relay, if any. Agreeing to run software and document problems with it is often *not* a job skill anyone is seeking. At least not for any kind of direct compensation. All software everywhere has beta testers... most often they work for free.

If it were me, I'd not bother with any type of formal disclosure. I may casually mention it if the topic were to come up in conversation, but I certainly wouldn't do anything like adding it to a resume, bid, pitch letter, or web site.