I'm not sure how far along you are with your web experience, so this answer may cover really basic stuff you already know...
1. You have to have web hosting
2. You have to export your game using that option from the file menu, ribbon or project bar - this will create the entire structure on your hard drive, wherever you choose.
3. At this point, what I do, is log on to my web host and go into cPanel, and using the file manger, upload everything that the export project created. The main files, the images folder (and everything in that folder) and anything else that export created.
Or you can consult thishttp://www.scirra.com/tutorials/74/publishing-and-promoting-your-construct-2-gamegazoogle2012-05-21 08:44:09