Tiny,
If you have not run nitrous before I would start with the 75 shot? Not having your engine setup for nitrous with 100 shot might blow a headgasket or damage pistons.
I would start with a search on nitrous in this forum, it has been covered many many times.
First what are your mods?
In general with a slightly mod GN (chip, air filter, adj fuel reg., adj boost, and a scanning tool (direct scan or knock gauge.) With a 75 shot you will see 2-3 lbs of boost jump. If running race gas a street chip should be ok ( you want 2-3 degree of less timing then w/o nitrous), a good fuel system (upgrade fuel pump like walbro 340), a way to watch for knock and if you see knock let off or you probably will be replacing headgaskets, normally you need to hit the nitrous just after you start rolling off the line or it will probably spin ( if you hit it right off the line it will spin even with sticky tires), leave it on (with no knock) the whole 1/4, set boost 2-3 lbs less then you would normally run, and you should see 1.5 second decrease in 1/4 et on a high 13 or low 14 sec. car. A faster car with see less improvement ( the fater your run the more hp you need to see the same improvement).
Chuck