To use Network Merchants as you payment gateway, log into your Bookeo Account. Click on "SETTINGS", then on "Online payments".
Select the "Payment Gateway" tab
then choose Network Merchants from the drop down list of payment gateways. Enter your Network Merchants API ID and API transaction key.
If you do not have a Network Merchants account yet, you can click on the link "Sign up for an Network Merchants account" to be directed to Network Merchants' home page.