If jailbroken... Install multiman, run and accept the agreements, press (Start + Select) and it will take you to the file manager. Double click (Yes I know your on a control, so press X twice or something) on the upperleft hand Icon and it will take you to the root of the PS3. From here you go to hdd0/game/BLUS30838/USRDIR/ and you should see EBOOT.BIN... Make a backup of this file (No Excuses here... you don't do it and something breaks its YOUR fault)!
After backing up the original EBOOT, have your file you want to replace the original with ready on a USB...
Put the USB in the slot that is furthest to the right, this will clear confusion as the slots are named differently, the rightmost one is USB000. Open the Icon in the upper left again... and open USB000 and you should see EBOOT.BIN in your root (if that is where you put it), press x Once on the EBOOT you want to copy, now press O and a popup menu will have COPY as an option, select it and press Square to switch to the alternate window, hover cursor over this window, press O then select PASTE. You are done!
But of course this is all after you install the updates in another section of this site that allows these mods to be active...
So, if you want it done right and you dont mind reading a bit, which I can see you do b/c otherwise you would not have posted a question as such, take a look around the site my friend...