The ground wire is connected to the ground bus bar, the neutral wire is connected to the neutral bar, and the hot wire is connected to the new breaker, which is then pushed into its slot.This situation is a little different from most houses.You can find electrical load calculators on line to help you with this.
Most panels are able to have a few extra circuits added to them.
You can check the load for your panel by using a 'load calculator'.
When you exceed 100% the breaker will trip as a safety feature. Even in this situation, it is a fairly big project.
You can do some checking on your own to see if your panel is large enough for an extra load.
The circuit breakers control the amount of power that flows into various areas of your home. See the articles 'Troubleshooting Electrical Repairs', 'Fixing Residential Wiring' and 'Basic Wiring for Homeowners' for a complete listing of all the electrical topics.
Before you add a circuit breaker you need to make sure that you want to attempt this type of project.
Why would installing a new circuit breaker be a needed task? The other scenario would be adding a circuit to your panel. For whatever reason you will find that this is not that difficult.
Your electric panel has more power coming into it than it needs.
This house has a 200 amp main breaker panel, which feeds 3 subsidiary breaker panels.
This is a good technique for house wiring, although it does cost a little more.
Working with an electrical panel can be dangerous and it may be impossible to completely turn the power off to the panel. As a rule a permit would be required before you perform this type of change to your home.