To access your SOS email account goto 
http://mail.saveourshotguns.org/Login.aspx

Use the full email address (not just the user name) and password that you received from the email admin.

You can setup forwarding to have your SOS mail sent to another account like gmail, yahoo etc. You would want to select to delete emails on the SOS server if you  don't plan on clearing out your SOS account periodically. 

To have the SOS address used by gmail for the sent from follow the link below for gmail specific instructions. Google the question for other providers.
https://support.google.com/mail/answer/22370?hl=en