If you are using RMXP all you need to do is:
1. Open up your game file
2. Go to file > Compile or Create GameDisk
3. It is going to give you an output directory in which the gamedisk itself is going to be saved. So if you want to access the file, you will need to go to that directory.
4. You also have the option to Encrypt your game data which secures your game file from peeping toms just in case you don't want anyone to look at your work. If you wish to encrypt your game data, then just check that box.
5. Click OK > and it will go through the process of creating a game disk. The speed of this is based off your CPU and how large your game is.
6. After that, you can go and register at a file uploading website such as MegaUpload or Filefront to host your game on. Register and upload your game through the directory that it is saved under.
7. Once the file is finished uploading to the site's server, it should give you a link. That link is to the direct page your game is on. Give that link to anyone that wants or you want to have the game.
I hope that clears everything up for you.
Cheers