Should take you less than 10 minutes.
Use this link to reach Equifax’s credit report freeze page. They appear to be offering this for free at the moment. Just fill out the forms and be sure to record the PIN they give you at the end. You’ll need that PIN to unlock your Equifax report in the future.
TransUnion has a (truly) free service called TrueIdentity which includes letting you lock and unlock your report at any time. This also lets you view your credit report at any time. They charge if you want to see your actual score. Sign up here. This looks very useful.
Experian charges $10.83 to freeze in my state. Your mileage may vary in other states. Here is the link to freeze your Experian report. They will also give you a PIN that you need to record.