To use Gmail to access your IMAP/POP email accountYou should have received an email with your account credentials:
Login to your Gmail account and click on the gear drop-down and select Setting, then select Account and Import from the options across the top...you should see the following screen:
Click on Add a POP3 email account you own and you should see:
Fill out the following form with your credentials, make sure the port is set to 995 and you check Always use a secure connection (SSL).
You can optionally leave a copy of retrieved messages on the server, but only select this if you are retrieving email from multiple email clients. You should also Label incoming messages to help identify them from your other email. You can use the email address as a lable, or you can create your own using the drop-down.
This option allows you to send email "AS" email@example.com (i.e. firstname.lastname@example.org in this example). The following setting let you set this up so email does not appear as sent on behalf of your Gmail account.
Uncheck the Treat as an alias and enter your new email address in the Reply-to address.
Enter the same credentials you used in the first part for the outgoing settings...make sure to check the Port is set to 587.
When you click Add Account, a confirmation email will be sent to your new email account, you can check this email online by visiting webmail.yourdomaion.com (webmail.matco.net in this example). You will see a login screen, enter your email address and password and click RoundCube, you will then see your INBOX, open the email and copy/paste the verification code, click Verify and you are almost done.
You should recieve one final email in your Gmail account asking you to verify the steps you have just done, click on the link in the email and you should be done.