combining song and apps of two people

I have an old mac computer and iPhone. All my apps and music are under one Apple ID. My wife has another old mac computer, iPhone and iPad. All her apps and music are under another different Apple ID. I just bought a new 27 inch iMac with High Sierra and I want to combine all our stuff on just the one computer and get rid of the old computers.

Can somebody give me some simple steps so I can see all our combined music in iTunes and make playlists with a combination of her songs and my songs? Right now, I can log into my Apple ID and see my songs and then log out and log into her Apple ID and see her songs. But I can’t log in to see both at the same time. I think this has something to do with Family sharing or Home Sharing but not sure which or how I would do it. I would then want to see these combined playlists on my iPhone and her iPhone and iPad

I would also like to share the different Apps we have both purchased. Problem is my new iMac doesn’t even list my Apps in iTunes like our old computers did. Is there a way to see these on my new computer and share them?

Thanks