First you must be logged in. Also, make sure a page for the game you want to add doesn’t already exist.
Under you user tools, click Create Content, then click Game.
On the "Create Game" page, there are 4 main boxes you need to fill out:
Original US Release Date (optional)
There should only be 1 page for every game, and if you try to create a Game that already exists in the database, you should get a warning message.
The only problem with this is that "Halo Reach" and "Halo: Reach" are different games (one has a colon in the title). Check out the list of all games in the WGG database to make sure you're not trying to create a game that already exists.
Here you can link the game to multiple platforms and genres using a very convenient auto-complete form. When you start to type the name of a platform or genre, it will generate a list of possible options to choose from. Click the name you want.
Linking a game to a platform will make the game show up on its platform list.
Here you can link the game to the developer and publish that created it using the same auto-complete form. When you start to type the name of a developer or publisher, it will generate a list of possible options to choose from. Click the name you want.
If the Developer or Publisher you want is not in the system, please make a forum post here so we can add them.
Pretty self-explanatory. GameFaqs has good release date information.
Here you can post some basic information about the game. Post some videos, a synopsis, maybe some pictures, whatever you want. Pretty soon, there will many more content types available for each game (like reviews, guides, cheats, achievements) so you don't need to put every bit of information about a game on this page.
Also, NO BLANK PAGES! Google hates empty or placeholder pages.
ANYBODY(!) can edit any game page, wiki-style. The site saves every revision, so if someone tries to screw things up it will be very easy revert to a previous version of a page.