how do you lot access archived gmail?

if you keep archiving things by accident it's probably the swipe. in the gmail app settings there's a swipe actions option, you can change it from archive to something harmless or turn it off. and if you want a view of only the archived stuff, search -in:inbox -in:sent -in:drafts and that's roughly it.

Archive doesn't put mail in a separate folder, it just takes the Inbox label off. Everything archived sits in All Mail. On a computer, All Mail is in the left sidebar (click More if you can't see it). In the app, open the menu and scroll down to All mail. Or just search for the sender or a word in the email, search covers archived mail too. To put one back, open it and use Move to Inbox.