If you are looking to make a donation to an online fundraising page, you can only do this by using a credit or debit card. PayPal is not a supported payment method at the moment but this may be something that is introduced in the future.
To make a donation by credit or debit card head to the fundraising page and click the Give Now/Donate button at the top of the screen. You will then be asked to provide the relevant personal details and the details of the card you would like to us.