I bought new brakes for the rear tire. They are installed but they are having trouble stopping the tire. Am i suppose to adjust that wire that brings the brakes to the tire rim?

How far does your brake lever pull when you apply the brakes? Should be halfway to the bar or less.

Here's a good guide that ought to help: https://parktool.com/repair/byregion.asp?catid=14

When something breaks on a bike you should have it repaired, especially with the brakes.

https://bicycletutor.com/sidepull-caliper-brakes/
https://bicycletutor.com/adjust-v-brakes/

Well, first, you adjust the pads so that..

Eh, go check the links that are already posted.