You will need to contact the IRS to have the letter re-sent, because the missing information, and all the instructions would have been on the letter.
Since the IRS cannot answer most phone calls, you might try the Taxpayer Advocacy Service, which exists to handle situations like this. Note that they may have an office in your state (whether or not it's open is another question). Even a phone call to the Advocacy Service may be able to get the IRS to send you the letter again.
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