Please list all parts
CPU cooler
Motherboard: Lenovo is7xm
Chassis/Case: If Lenovo, Small form factor or MicroATX size
Well, Lenovo is7xm is an OEM board, it has a built in backplate designed to accommodate the included cooler only, Dell and HP also do this often. This must be removed to install an aftermarket cooler.
If you have purchased something like a stock intel cooler or equivalent with push pins, should just be a matter of taking the motherboard out, removing the backplate and installing the new cooler.
If your new cooler comes with a backplate it will need to be used in place of the original one.
Not sure how easy it is to remove that backplate, never needed to on an M92p system. (in the case of Dell, it is also part of the CPU socket)
Another option is to get a more simplistic cooler, like a Deepcool Gammaxx 400, all you need to do is get 4 screws that fit the existing mount and some washers.