In most cases, when it’s too good to be true…then it normally is. A good way to check would be to first analyse the site and ensure it is in fact indexed in Google. There is no such thing as “Instant Riches”. I agree with Satrap, if you want to make a lot of money online then you’re going to sacrifice the needed time. Making money online is an art, not a contest.
You can pick writing jobs directly from a live job board or have to bid on a job and hope that the job is awarded to you by the relevant client, depending on how the site works. Some sites may require you to take an English grammar and writing test and some may require you to submit a sample or samples of your work while others may require you to take a grammar test to evaluate your skills. If you pass any relevant test, the relevant site will let you take on writing jobs.