First you need to get registered with some companies, then request or self assign work, then once you have a shop awarded to you, read the instructions thoroughly. Some companies will have you test first for jobs before you can request or self assign them. Then you are ready to perform the job at the location assigned, during the time frame assigned and get your report and proofs of visit in before your deadline. During usually 2-3 days after you put in your report you may hear back from the report editor for items that need to be clarified or expanded on. Once the shop is accepted, some companies will notify you of a score on the shop or post it on their website. Then you wait for your payment/reimbursement, which may take 2 to 16 weeks, depending on the company you did the job for.
I would suggest you read through the threads at the top of this section of the forum for getting yourself set up to shop.