First, you’ll want to use the import step Use Excel file to upload the file with order payment information.
Then you’ll want to use the import step Pull from Shopify to pull in your orders. Depending on what product information is in your excel file (line items versus orders), you’ll want to specify this in the Pull from Shopify step.
After these imports, you’ll use the step Combine tables to join the two datasets based on a column that exists in both datasets.
The last part of the flow will require a bit more work. You’ll end the flow with the step Send to an API. Follow the steps 1-3 seen here to get the credentials set up:
Once you have your URL from the credentials page, modify it to end in /admin/api/2020-10/orders/{Id}/transactions.json. If you originally pulled in your Shopify orders with line items detail, then change {Id} to {Order: Id}.
In the Body section of this Send to an API step, put this:
In the above example, the currency is set to USD, so adjust as needed. The amount field needs to reference a column, so replace what is inside the curly braces with the name of your column. The kind section is set to sale since it seemed most applicable to your use case. You can see other kind options in the transaction properties table here: Transaction