Welcome, @Ahmer
Your reference file is the correct data to use but it must be in an uncompressed format. You can uncompress it using the convert function under the pencil icon. FAQ: Converting the file format.
Then, to test if the problem is with the database options, you could grab a copy of the version used with tutorials from here and see how that works. If it fails, then you’ll know the issue is with the other inputs, or possibly the parameters used. Tutorial version of Silva (this is a full release, just not the bleeding-edge brand new release! 
) → Hands-on: 16S Microbial Analysis with mothur (extended) / 16S Microbial Analysis with mothur (extended) / Microbiome
If that is not enough, what is the error? We can probably help to solve it. How to share your work is in the banner at this forum, or see here directly for the instructions. → How to get faster help with your question
Let’s start there, thanks!