How do i set up my default mail client on windows 7

Please dont type in all caps
It is considered shouting :)

What email program or service are you using?

For example in Microsoft Outlook you would click on insert icon on menu bar
and then browse or look for the location on the hard drive the file is in
then select it

similar in other email managers
might be called "attach" or "insert" etc

also you will be limited in the size of file you can send