First, Login to your SalesNexus Account here
Once logged in, click the "Manage Account" button on the upper right hand corner of your SalesNexus database, to the right of the Quick Search bar.
From one screen you can Monitor Subscription Status, Manage your Subscription, Update Account Details, and Add a Payment Method.
To add a payment method to SalesNexus, refer here
If you would like assistance with Managing your Account, please reach out directly to firstname.lastname@example.org