How to reset the username and password in ignition vision client
Welcome, you haven't stated which version you are on.
Did you explicitly mean in a Vision client or for a Vision client?
https://docs.inductiveautomation.com/display/DOC81/Managing+Users+and+Roles
If in then there is the user management component.
If for, then there is a section in the gateway you can edit, also described in the above link.
This assumes you are using the standard user/roles security and not another feature such as IDP.