Welcome to Catholic Answers Forums!
I am sorry you have encountered frustration so early. This is a complex site, and learning its eccentricities can test our patience sometimes.
Unfortunately, the problem you are having with your signature is due to your newness here. Currently, you are considered to be a Trial Member, and as such you have not yet been granted signature privilege.
You will be able to have a signature once you achieve the rank of New Member. This will happen automatically once you have been here for approximately 3 weeks and
have made at least 15 posts.
More information on the membership ranks can be found here.
I'm sorry to bring you bad news, but hope you will stay with us. We get better with every new member who participates in the discussions.