Hello' It depends on the device you are using:
- On most android phones you have to press and hold the power button + the volume down or press and hold the power and choose screenshot on the pop up manu.
- For computers you have to press Ctrl + prt sc keys together, open paint and paste it (Ctrl + V) it' you will then save it from paint or any other image editor software. You will please comment below for further assistance.
- You can also install and use a browser plugin/add-on like 'Awesome screenshot'.
- Lastly, depending on the bank you are with, you may have a 'Print' or 'Print receipt' button on the webpage that displays following payment - you can then us that to print a more formal proof of payment.