...
The Blastp app takes a folder as input for the database because there are multiple files involved. The best thing to do when you are creating a database is to give the database and the output file the same name e.g. "mygenome". Then after it has run, make a new folder inside the output directory, name it "mygenome", and drag all the database files into it, except but not the logs directory. You can then drag that directory "mygenome" to one of your other directories so it will be easy to find. When you run Blastp, drag and drop the database directory you created into the database input for Blastp.
...