Login to your paypal account
Click on Merchant Services
Under 'Create buttons' section, click on 'Donate'
Under 'Organization name/service' type your company name
Scroll down to the bottom and click 'Save Changes'
Click the 'Select Code' button and then paste that into an email to us.
That's it.
Of course there are many things you can do to customize the button, so feel free to do so.