By default, all new users will have a trust level of zero, and will not be able to create new topics, post images or attachments, and other things that might be spammy.
User trust levels are a way of…
Sandboxing new users in the community so that they cannot accidentally (or intentionally!) hurt themselves, the forum, or other users while they are learning what to do.
Granting experienced users more rights so that they can help maintain and moderate the community they generously contribute so much of their time to.
All you have to do is spend some time looking around before you make your first post. To be more specific, you need to spend a few minutes looking at existing topics, reading posts, and just generally looking around. The threshold is actually quite low, so it shouldn’t take long at all.
For a more expansive description of Trust Levels check out this post by the Discourse team. We are using slightly lower levels than the ones they use, but similar.