As of today, residents can request free at-home COVID-19 tests now that the U.S. government has launched an online sign-up system.

Anyone who visits COVIDTests.gov can access a link to a request form on the U.S. Postal Service’s website.

Any household in the U.S. “can order one set of 4 free at-home tests,” according to the webpage. There is a limit of one order per residential address. Each order includes four rapid antigen COVID-19 tests.

The USPS said it expects to start shipping the tests in late January.

White House press secretary Jen Psaki told the Associated Press that the website was in “beta testing” and operating at a “limited capacity” ahead of its official launch on Wednesday.

The tests are part of a program that President Joe Biden announced last month to purchase and distribute 500 million at-home tests. That number has since been increased to 1 billion.

To get the tests in time to meet CDC guidelines on when people should be tested, people should sign up early—before a suspected exposure.

The USPS said tests will ship “within 7- 12 days” of ordering, according to the Associated Press. And shipping is expected to take one to three days.