Using Paypal without an account:

You will see at the top of the screen, this menu. Enter your donation amount in the white box:

It will now look like this. Click the blue "Update Total" box:

You will now see the top of the page change so that it is one line.

On the left side of the screen you will see these words:

Click on the words Continue that are underlined (right above VISA, Mastercard, etc logos)
You will then come to this page:

You can now enter your information and check out.