People who signed up to have their tax returns deposited into their accounts via direct deposit have begun receiving their stimulus check.
However those who receive their tax returns via a paper check will have to wait a while, as the checks are expected to begin being mailed the week of May 4th. At that time, the IRS will send them out at a rate of five million per week, for up to 20 weeks, with the lowest income individuals getting theirs first.
If you want to give the IRS your direct deposit information to receive your check sooner, they have set up a portal to allow you to do that. Simply go to https://www.irs.gov/coronavirus/get-my-payment to get started.