If you need an ISRC for a recording, you can use the Registrations Module to get one.
Use the "Add Registration" button to begin.

Click on the "Get an ISRC" card.

Then, select the track that needs an ISRC from the list. Only tracks that do not already have an ISRC assigned will appear on this list.

Confirm that the Primary Artist and Track Title are correct.

Solo plan subscribers will be charged $1 per ISRC. Team, Business or Enterprise plans get unlimited free ISRCs. 

Once you confirm the information, an ISRC will be assigned and the Recording Details will reflect the assigned number. 

You can also view the ISRC by looking at your list of completed registrations and viewing the record for that recording.

If you already have an ISRC for a recording, you can simply add it to the Recording Details page. You should be able to find it by looking at your account with your distributor (TuneCore, Symphonic Distribution, CD Baby, etc.) or by asking your label.