My professor told me that MySQL and PHP were installed in their server, but not configured and for LS I need to configure them. So my question was: how do I set them up? I ask this in this forum because I think I have to modify some files inside the LS folder and I hope someone can be of help.
This has nothing to do with Limesurvey. You will need to create a working LAMP (Linux, Apache, MySQL, PHP) environment on the university server, if it has not been set up already. I think this is a little bit above a normal survey creation.
I think your professor gave you a lot of bad advice.
The XAMPP enviroment is great for testing, programming and local development of surveys, but it is not good for "production".
So you should transfer your survey via LSS file to a LS installation that is available on a webserver. Your professor gave you access to a server, but without a LAMP environment, which you would have to set up now.
There are a lot of explanations on how to setup a LAMP environment, but honestly, I don't think it is a good idea. Because you obviously don't know what you are doing (no offense, this is nothing that everybody would need to know) and setting up a webserver without some knowledge can work, but creates quite some security issues, I think. I personally wouldn't want to setup a webserver for production, there is just too much involved that can go wrong in my opinion in terms of data security.
I personally would recommend to get a good shared webspace or a VPS with a admin software (e.g. Plesk or Cpanel) and go from there. Yes, this would involve some costs, but I wouldn't recommend a newbie to configure a webserver to run LS on for a production survey. My honest opinion.
Now, if you really want to go down the route of setting up a webserver on the university server, you will need more than the FTP-Access, but access via command line to setup and configure PHP/MySQL. I highly doubt that the administrators of the server will grant you this access, because you could do much more than just setting up PHP/MySQL. If they grant you this access, there are a lot of tutorials out there on how to setup a LAMP environment. But as I said, this has nothing to do with Limesurvey itself (besides that LS requires a working webserver with PHP/MySQL to run).