Your computer is not on the same network as your phones cellular network. I believe you will need a static IP number for your computer to allow access to the computer from outside of your home network. Your phone's cellular network will use the internet to connect to your computer. You'll probably need to work through your ISP to make this happen.
It's not required to have a static ip address. If your internet service provider changes your public ip address then you will have to use the new ip address to access your files. If you were setting up a site that needed to be up all the time then you would need a static public ip address.
You need to setup port forwarding on your router. You will forward port 5003 to your host computer local ip address.
1. Obtain you local ip address : When you turn file sharing on FM displays your local ip address. for example 192.168.1.10
2. Enter your rounter ip address into your browser to configure your router. for example 192.168.1.1
3. Go to your port forwarding settings . Add port 5003 and have it to forward to your host ip address
and set protocol to both.. example from step 1 : 192.168.1.10
4. Go to a website such as http://www.ipchicken.com/ This is your public ip address assigned by your internet service provider. This is the ip address you will need to use.
5. If you have any firewalls enable then you will need to open port 5003 on your firewall