Creating a finance app

I’m trying to create a finance app that allows users to select “Income” or “Expense” from a dropdown and input a memo that stores along a numerical value like any finance/banking app. Then I need to be able to repeat the process and keep a running total of all the funds. I can’t seem to figure out how to do this. Could someone help?

What have you tried so far?

I created the dropdown box and created the workflow for selecting income and selecting expense but I’m not sure where to go from there