Actually, it's fairly easy. To start your case, you'll have to file a complaint or claim. Most states have all the forms and a lot of free self-help information online on their small claims court information website. You can also call or visit the small claims court where you plan to file your claim.
Some courts allow you to fill in and file your forms online yourself or through an approved online service provider. In other states, you'll need to fill out the forms and mail or deliver them to the court.
The information required is generally straightforward. Just follow the instructions that come with the forms and use any self-help online resources available. That should be enough to get your case started.
If you're a little unsure about how to proceed with your case, you may be able to bring a lawyer on board as an informal "coach" (not as official counsel). Learn more in Nolo's article Hiring a Lawyer as Coach.