Hi, and welcome to the forum. It's good to "see" ya!
When it comes to e-mailing attachments, you have to think oppositely from using a computer in that you have to be in the app that contains the file versus being in an e-mail program and finding something to attach.
So, for example, say you want to e-mail a photo. Go go to the Photo app, select the photos to mail and then an e-mail pop-up appears for you to fill out the info to mail those photos. This process happens in other apps, too, such as word processing apps, text apps, ebook apps, etc. It's a function of Apple's sandbox design in that an app, even the stock ones, can't go into another app's files. It's a security thing...
If you have a specific app to mail from and if this explanation didn't help, do ask for more specific help. Otherwise, hope this clarifies.
Marilyn