Please link to the product you bought. I think I know what you did, but I want to be sure.
If you bought these:
http://www.ebay.com/itm/08-09-10-NISSAN ... 17&vxp=mtr
...then you do not install a bulb into the area where the OEM brake light bulb goes. There should be a harness inside of the tail light in that opening. You plug the harness from the tail light into the socket where you would place the OEM bulb, and then twist the socket in to simply secure it in place.
If you did what I think you did, you have an LED bulb working on the inside of the tail light. It isnt visible on the outside because it is blocked by the LED array in the after market housing. These sets do not come with bulbs. You swap over the OEM reverse, turn signal, and side marker bulbs and then connect the harness like I stated above. The OEM brake signal bulb is discarded.