iam from pakistan sory my english bad soo i just installed call of duty black ops 2 when i double click nothing happens on screen and when i typed on google about this problem answers was steam i dont knw what is steam y steam iss needed to play cod black ops 2 i dont knw whr to get steam i dnt knw how to play game without steam plz help frnd
and second problem is when i play bf3 it ask for activate ur game he ask for product key i dnt knw how to get this key is it freee if free send me plz i will b thankfull 2 u if u hav solutions to these to games
It is potentially likely that you did not receive legitimate retail copies of the software in question (perhaps through no fault of your own; counterfeit software is a problem modern consumers face, especially PC software).
Regarding the applications in question:
Steam based games must either be purchased on Steam, or provided with a Steam activation key (e.g. if you purchased the game at retail). Steam is Valve's online content delivery service, the client itself is free to download (and should be installed alongside retail software that requires it, however if you simply missed this step of installing Black Ops 2, that is understandable (as far as I am aware you are allowed to refuse installation, but it renders the game unplayable as it relies upon Steam for copy protection, updates, etc)), from Valve:
Battlefield 3 will instead rely on EA's Origin (similar in nature to Steam, but provides EA content and is supported by EA):
Again, if you simply failed to install that application while installing Battlefield 3, it would render the application unplayable. In both cases, however, you should have activation keys within the product packaging (usually they're included as a separate card within the game box, or printed within or on the cover of the game's instruction booklet) - these keys will be needed by Origin or Steam to validate the game and allow use of the software. If you didn't receive these keys, and purchased the software from a legitimate source (e.g. GameStop), contact customer service for each game's publisher (this information will be listed on the game's instruction booklet as well) or the retailer where you bought the software - it's a relatively rare problem that activation keys are not included in packaging, but it does happen from time to time (some retailers also inadvertently remove this material when repackaging software (e.g. to remove expired promotional content)). You will likely be asked to verify that you purchased the media, for example by providing a receipt, in order to receive support. There is no mechanism for me to provide this kind of support; it has to come from the software publisher (because they issue the licenses and product keys).
These keys are certainly not free or public domain - they are a copy protection mechanism to ensure that the content is protected, and to ensure that you are using genuine software. Essentially when you purchase a game, what you're buying IS the key, which allows you to use a copy of the application you've selected.