Navigate to the Missing Transaction that you'd like to populate in iDonate. 
Payment > Payment Transactions > Missing Transactions

You'll see a message, "Are you sure?" Click, "Yes." 

The record will now be listed in GMSNext and in the org's iDonate back office. 

Great job, you've successfully created this transaction!

Idonate

Sometimes gifts from iDonate don't be posted to the iDonate back office correctly, and get put in the Missing Transactions section in GMSNext. While looking at the record, follow the directions below to 'create' the transaction. 

Internal: How to Create a Transaction from Next: Missing Transactions