To be honest, I’ve never use this mode before. So I’m not so sure what kind of command is it. But I believe that the command is for creating the file. You should be able to run that command on your laptop, and then upload the resulting file to “specific path” shown on the instruction.
Okay, I’ll try it out later today when the beta goes public.
Hopefully I don’t run into any problems, but if I do, I’ll be back. 
For domain validation in manual mode, you don’t need to have SSH access to the server.
For each domain, you need to create a file in the directory /.well-known/acme-challenge/. The filename and contents are given in the terminal.