Within the body of any page you are editing add the following text;

[ paypal : XXXX ]    (without the spaces!)

Replace 'XXXX' with the Hosted Button ID. You can find the Hosted Button ID within the code given to you by PayPal, the line you are looking for should look something like this;

and the ID is the value ie 'QWXTRGFHFDVSD'. So the text to add to create a paypal button for this example would look like this;

[ paypal : QWXTRGFHFDVSD ] (without the spaces!)

And the button will then look like this;