You should receive a Notice of Audit letter by mail, which will give you information about your audit. It should include details about the items that are being reviewed on your tax return, the records the IRS will need to review, and the deadline for the documents requested. This notification will go to your last recorded address, so be sure the IRS has your current address on file.
Keep in mind that the IRS will never call or email you. Be wary of any “audit notices” that come through via phone call or email.