How do projects work?

Projects matching your skills are displayed in your project list, under "Find an opportunity". All the details are in the job description–if you like what you see, click accept and start working.
Projects usually involve delivering a clearly stated result or objective, which is communicated to you via the briefing. For example, "Write a blog post about freelancing in under 1200 words". Projects also have clear deadlines that you need to adhere to.