On the SoFi mobile app, select the Invest icon from the footer menu. Then, select the Invest account you would like to contribute to. From there, select Add Money. Enter the dollar amount of your contribution, select the source bank account, confirm the Invest destination account selection, and set the frequency to one-time. From there, select Next > Confirm.
On SoFi.com, select Invest from the header menu. Then, scroll to the Invest account you would like to contribute to and select View Account. From there, select Add Funds. Enter the dollar amount of your contribution, set the frequency to one-time, select the source bank account, and confirm the Invest destination account selection. From there, select Review > Add Money.