Create a shared folder and allow wife to view on her phone

I;ve done this several times but I'm looking for detailed cheat sheet on creating a shared folder on your phone and then how do I get files (picture,video) into that folder so my wife sees on her phone. Are they stored in icloud or on phone?

I've got 15,000 photos set up this way she can view, but I've gone brain dead and cannot remember how to do it. The files reside on a Windows 10 Dell laptop. any help would be GREATLY appreciated.

Thank you very much

Brad Burnett/SC