how do i use the serial number i have a real disc for?

[llcools]

im new to steam, how do i add a game using the serial number i have a real disc for?

[Falro the Great]

Click "+ Add a Game" on the bottom left of the Steam client, then "Activate a Product on Steam". Keep in mind though, some retail games cannot be activated on Steam.

[#DADAN ~ iPANiC]

In the bottom left corner of Steam, there should be an option to "Add a game..."
Then just choose "Activate a product on Steam", and you should be able to enter your CD-key. :)

[llcools]

its sims medieval, i know you can get it on steam. So do i add it as a non-steam game as i have the disc or activate a product on steam? sorry im such a newb

[llcools]

oh thanks x

[Falro the Great]

Just click "Activate a Product..."

[llcools]

now it says invalid product code, any ideas?

[Falro the Great]

https://support.steampowered.com/kb_article.php?ref=7480-wusf-3601
This is a list of retail games that can be activated on Steam. If it's not on there, I'm afraid we can't help you.

[llcools]

guess i'll just play it normally then, thanks for the help guys

[Tev]

You can still have it as a non-Steam game and thus have the screenshot, in-game overlay support, et cetera.

Add a Game -> Add a Non-Steam Game
Locate the executable and add it, you can rename the 'Sims3Launcher' (or whatever it was by default) to 'The Sims 3' when you right mouse click it and go to Properties on the Steam -client.

The reason the CD-key doesn't work, is because Sims isn't a Steamworks - title. The only way it goes through the Steam -client is if it's bought from the Steam Store directly, and only then do the DLCs from Steam Store work with the basegame.