If you're going to be running Linux, you really need to learn the Command Line Interface (CLI). Unlike Windows, the CLI is your friend in Linux. You can't really support a server without it, you can't SSH into another computer with out it, and there are tasks that you can't do otherwise. Here's a link to an online book about it, I think you should read.
http://file.allitebooks.com/20190304/The Linux Command Line, 2nd Edition.pdf
In my last post, I provided you a link on how to set it up. I said it was for setting up multiple FTP'ers, but it's a step by step instruction doc on setting it up from start to finish. Go to
https://articlebin.michaelmilette.com/setting-up-openssh-sftp-on-ubuntu/.
For most anything on LInux, you can do an online search for 'how do I install/configure/do ______ in Ubuntu/Linux'. There are thousands of articles explaining how to do almost everything in Linux. I use
www.duckduckgo.com for my online searches. They respect your privacy and don't track you like google does. If you get stuck or don't understand what the website it telling you, ask us.