What tags are you referring to ?
Click on edit next to the topic's title. There you can add/remove tags.
Sorry, tag editing is restricted to higher trust level users. I'm not sure if you can add them when you create the post thread or if that is restricted as well.
Thanks, I now just need to become a higher trust level user
try the pen edit and their you can tag by @________ type the user name in the space.
hope i am helpful.