[galaxy-dev] How to add megablast database?

Hi, I am using local Galaxy on my computer. I would like to use megablast but I don't know how to add wgs and nt database to local galaxy (I am new to galaxy). 1. Where can I download those databases (if you dont mind, can you give me the link?) ? 2. How can I add those databases to galaxy? 3. What if I want to do BLASTN instead of megablast, how can I do that? Thank you very much,