In order to connect your Royal Mail Click & Drop account to Smartcode you will need to login to Click & Drop with your Royal Mail credentials.
Once logged in navigate to 'Settings' then 'Integrations'
Then tap 'Add New Integration' in the top right
Then select 'Click & Drop API'
You will then be prompted to enter your details, once complete click 'Save'
The Click & Drop API entry will then be available in your integration list
Tap on the entry to reveal your API key which you can then copy