if you want to use paypal in your cms, you have to setup your payal gateway settings. Go to “General settings>Payment Gateway Settings > paypal settings”.

you have to create an app for paypal api, you can check this article for know more about create app in paypal.
Create or edit sandbox and live apps

Here is paypal supported Currency List, if your currency is not supported by paypal, then this cms will charge them in USD as per your give conversation rate in currency settings.