Select Account Settings

Select Add Mail Account

Enter the login details of your Email account

Click Continue and allow Thunderbird to find your account settings. Press Done

Thunderbird does not like sites which reside on shared servers and presents a security warning. There is no real security issue here, so go ahead and click Confirm Security Exception

Now go back to the account settings and change the email address to be your personal one, rather than the one used for login. You might login with but use to answer emails.