With Stripe you're able to send a link directly to your customer allowing them to add their credit cards themselves to your Customer card in Qondor. This article is a guide for you as a Project manager, if you want to send a guide to your customer please use this article regarding adding a credit card in Qondor.
From the Customer list, click the credit card icon:
In Customer credit cards you can click the "New card" icon to add a new credit card:
Enter the credit card details and add an internal note:
The default card has a green border to indicate that it's the default card. If you hover a card you can set this to default, delete it, and view the note.