Lagering (conditioning) takes place after your carbonation is set, and is merely allowing the beer to age for a while to allow the mature flavors to develop and overtake the young green apple, yeasty flavors that are hallmarks of a young beer. You can condition in a cool or cold environment. Most of the time, in the refrigerator is best if you have the space. The depth of flavor develops better in this temperature than in a warmer environment, but if you have to opt for shelf space rather than fridge space, you can just give your bottles as much time in the fridge as you can.
Do not condition your beer for more than 4 months unless you had added additional ingredients to make a stronger and/or hoppier beer. If you are making a beer with added ingredients, you can wait for up to six months before drinking.