Adding a PayPal button in WordPress is quite simple.
First you need to obtain the HTML code for your button. This can be done from the official PayPal website.
Once you have the code for your button, log in to your WordPress admin area and go to Posts > Add New. Switch from Visual to HTML and paste the code for your PayPal button there. Publish your post and you will see your PayPal button in it.
If you want to see a video tutorial on how to add a PayPal button in WordPress, click Play Video on the screen below.