A credit card linked to the bank account of your company does not need to be reimbursed to you. Therefor the administrator of the company account will create and manage these payment methods for you.
All personal (and thus reimbursable) payment methods you want to add on top of this, you can create via 'Personal Settings' > 'Payment methods'. 'Cash' is added already by default.
After clicking on the button 'Add payment method', you can fill in the needed details:
By clicking on a payment method the detail will open, where you can indicate it as your default payment method for all expenses. This means the payment method is always automatically filled in for you - but still changeable of course, whenever needed.
You can deactivate a payment method when it is no longer relevant, so that it no longer appears in your payment options when adding new expenses. To do so you just untick the box before 'Activate'.