First of all login to btccpay.com and click on the create widget button, if you dont see the button or the domains and wallets sections are empty you have skipped the setup guide here.
Now we will enter the variables for our pay with BTCP button, the entries for domain name and wallet leave as is unless you have multiple domains and wallets under one account, if so just select between whichever.
Give your button a name, maybe use what its for for easy tracking and set your confirmations to approve to 6 (standard confirmation count for btcp tx) and under internal notes add your own details.
Select a button style from the list and click create and get code
Once you have created your code, simply copy and paste it into the page you want it to display on, where you want it to display.