Sometimes the best way to collect money from your site's visitors is through a Paypal button.
This works well for registrations requiring more information, or collecting donations without a set amount (aka, allowing the donor to choose the exact amount they wish to donate).
The first step is to create your buttons in Paypal.
There is information on how to do this here.
The step about "select code" allows you to copy the code you need for your site.
Next, go to the page on which you want to place the buttons.
Click on the edit tab of the page, and scroll to the text editor. Click the "source" button on the text editor. this puts you in the mode where you can enter code.
Paste in your paypal code.
Click "source" again - a box should appear where your button is. It may look a little strange, but once you're viewing the actual page, it will look normal.
Save your changes, and then view the page.
Note: you can embed buttons any where a text editor is available - this includes blocks.