The process to apply for a VISA card is quite simple, and it is similar to get add-on card.
1. Login to Karbon Dashboard
2. Click on Team ( left side )
3. Click on the User to whom you want to issue a card
4. Click "Add a Card", select Card Type, and click Submit
After this step, the Karbon Ops team would review your application and issue your card in 1-3 working days.
The below link describes limits set on your Karbon Cards, and how to modify them later.