Sign into your ecommerce store
Go to Woocommerce -> Settings -> Payments
Find the Paypal Standard payment option
Tap ‘setup’ or ‘manage’ on that line
Complete the settings as noted in this image. Note that you will need to sign into your Paypal account to complete the last fields in this page.:
Sign into your business account with Paypal as normal.
Click the gear icon (settings)
Choose the ‘Account Settings’ option
Choose API Access
You will click on the ‘Show’ link for each of the three fields shown below, one at a time. When the values are shown, you will cut-and-paste them one at a time into your ecommerce store where shown in the woocommerce image. When complete, you will save the settings on your Paypal Standard page.