it would be helpful to know what software you're using to create your site.
You'll need to register with PayPal before they can accept payments on your behalf, and then their site will generate html code which will create 'Pay now' buttons for you. These will contain links direct to Paypal's site, and the code will tell their server which products and prices are involved. All you have to do is create a product catalogue with a PayPal button for each product or service.
If you don't have many separate items you can create the catalogue in a simle table - the PayPal site (to which your customers will be taken) has all the necesary forms already set up.