Welcome to the forum Salts155.
As has already been mentioned if you want to really make a hobby of keeping fish you don't want your first experiance to be dying fish left, right and centre. Not to mention the welfare of the fish!
To avoid this you really need to do a little reading, there is a good thread available
HERE that can run through the basics.
Basically you need to 'cycle' your tank before you add any fish to the system, while fish can cycle the system for you it very often results in the death of fish(s) and is certainly very painful for them to live in your tank while it cycles.
You can 'cycle' the fish before adding them, that will give you time to read up on what fish to keep and learn more about the hobby, it does take some time but it's worth it in the long run! (Just finished my fist tank 1-2 months ago and all fish still here!)
Nearly everyone on this forum will tell you to fishless cycle, to read how to do that, check this thread:
HERE
If you insist on a fish-in cycle then you can get some guidance
HERE
Typically those 'booster bacteria' products do very little, if anything!
All the best,
Sean