Hello Silav,
You can post messages to the group without joining it, as you have
already discovered, you might still want to join the group to
receive messages from the group by email.
When you visit the google group page, there should be a button
"Join Group" that you can click. You probably need to sign in
first, using a google acount. If you don't have a google account
you can create one (from the Sign in page). You can use your
existing email address, or create a new gmail address when you
create the account. (I vaguely remember that there was a problem
in the past using @
student.gu.se email addressess when creating
google account, hopefully that has been resolved now.)
Best regards,
Thomas Hallgren