You have to think in an opposite fashion when using an iPad to mail files or pictures. Instead of being in the mail program and grabbing a file or photo to mail, you have to be within the app (like Photos) and open the mail app.
So, for example, if you want to mail a picture, you must be in the Photo app. Then, select the curvy arrow on the upper right, select up to five pictures by pressing on them and then, in the upper left should be a Share button. Press that and one of the options should be to e-mail. Press that and a pop-up e-mail window should open for you to fill in the e-mail details and your message.
Most other apps have the same capability to e-mail stuff from within them.
Again, it's just the opposite of how you've done it before on a personal computer. Hope this helps.
Marilyn