Open the email message.
Is the picture displaying in the body of the message? If so, scroll down further. You are looking for the picture (or the paperclip icon) as an "attachment".
Tap that icon or the image. It should expand to fill the screen.
At that point tap your menu icon (it usually looks like 3 or 4 horitonal lines, i.e., like a shrunken menu with line of text).

There should be an option to Save the image. Select that and Save it.

If there is no menu icon, your phone might respond to holding your finger on the Open image and a menu pops open with an option to Save.

LMK if one of these works.

Jim