I am pretty sure that you can't. Do you have a Blade Hooligan or a Supercycle Hooligan?
I think you either have steel rims, really bad v brakes or they aren't adjusted correctly. Well adjusted v brakes can stop practically anything.
1) Look more closely at the frame near the rear wheel. Is there a tab welded to it about 3" long with 2 holes on the left (non-drive) side of the frame? If not, you don't have disc brake mounts.
2) Check the hubs (the things in the middle of the wheels)... is there a flange on one side of the hub that has holes for 6 bolts? The front wheel might have it on either side but the rear wheel would have it on the non-drive (no gears) side.
3) Look at the fork on the left side. There should be one of 2 things... either a tab similar to what would be on the frame near the rear wheel or 2 posts with holes in them. If one of these things aren't there then you can't mount a disc on the front either.
I can't think of a single example of a frame weighing 47 pounds, or any entire modern bike for that matter with the possible exception of a high end downhill bike which would already have discs. I'm sure you must be mistaken.