but I will use Apple's Mail app as an example.

1. With the Mail app open, create a new email.

2. Find the icon of a Paper Clip, click it, in the resulting window, navigate to where your JPEG is located.
3. Click it and choose Open or Choose File
Done.

Or

Step 1 and then just drag your picture into the new email
Done

Or

Step 1 then press Shift + Command + A

Or

Step 1 then File (in the menu bar) > Attache Files

You will find the Help button very helpful for simple thing like this.


P