Welcome to the forum 
The reason you cannot create a topic is that you are not at Trust Level 1 yet. Once you reach Trust Level 1 status, you can then create a topic! You can refer here for more information: Trust Levels and How To Advance
Achieving Trust Level One is easy. The criteria is:
- Enter 5 Topics
- Read 5 Posts
- Spend at least 15 minutes reading posts on the forums
Once you do that, you will receive a Personal Message from the system saying that you have been upgraded to Trust Level 1 
The download link, did you get the sim via the Microsoft store or Steam?