If you have JRemote working on your local system then you just have to set up your network so that JRemote can access your files from a remote place. Unfortunately, that is not something that Media Center can set up. The setup varies depending on your Internet service and your Internet router.
You need to set up something called "port forwarding" on your router. Port forwarding allows you router to connect an outside client (your phone) to our computer running Media Center. The port that Media Center typically uses is 52199. So, you need to tell your router to forward port 52199 to your computer. (You can change the port number in the MC Network setup but most people just use 52199).
If you have a standard Internet provider like Comcast, there are explanations online for setting up port forwarding. If you cannot find the instructions online for your specific Internet provider and router, you might ask their support line for help. If you have a friend with technical expertise, they may be able to help you set this up. Or, if you post the name of your provider here someone may be able to provide you with instructions.
Once you have port forwarding set up you can go to this url from your computer to see if it is working correctly.
https://canyouseeme.org/Porting forwarding does make your system slightly vulnerable to outsiders getting into your system, but it is a very minimal risk. Many Media Center users use it with no problem. I would not worry about it, but you should know that there is a very small risk involved.
You may also have to set up Windows Defender to allow MC access through the Firewall. You can do that in the Defender app under the Firewall settings.
This will take some effort the first time you do it, so be patient - and ask for help.
EDIt : There are YouTube videos on Port Forwarding for many different routers and for services like Comcast. Just search for them.