Yes, as already replied. If your desktop has a wifi card built in it's just a matter of turning thr wifi on locating the hotspot you have the password to an logging in.
For a 4G Broadband stick. My experience is that you will need to load a program to your desktop from the company you got the stick from. When you want to use the stick. Plug it in to the usb port, start the software, wait for the stick to be recognised, you may have to enter the password and you should then be connected wirelessly to the Internet.
Hope this help!