Hi I have received an Invoice I need to pay to my email.. how do I forward that to my quickbooks? Or do I wait to receive a receipt?

Look no further, @tolley-kayleigh-.

You can add the transaction to your QBSE account once it is posted to your bank account. Follow along below to do this right away:

1. Go to the Transactions menu.
2. Click the Add transaction button.
3. Enter the Date, Transaction Type, and Amount.
4. Once done, select the appropriate category.
5. Then, hit Save. 

For your reference, please see this article: Manually add transactions in QuickBooks Self-Employed.

Also, here's a great source that you can open to guide you in using Schedule C form to report your income and expenses: Categorise transactions in QuickBooks Self-Employed. 

Don't hesitate to post here again if you need further assistance in recording your invoice in QBSE. I'll be round to help. Have a good one.