Yes, you can still use your Keepit username and password to sign in to Keepit even after you set up SSO. To be able to sign in with Keepit credentials, you need to disabled the Make SSO mandatory option in the SSO configuration. If it is disabled, each time you sign in to Keepit you will have the option to use either your Keepit credentials or SSO.
Please keep in mind that if SSO is not mandatory, then you will not take advantage of the convenience and security benefits of SSO.
When setting up SSO, we recommend you create an SSO Admin who will be able to sign in with his Keepit credentials even when SSO is mandatory. The SSO Admin is a user role that does not have access to users or users' data but only to the SSO configuration. If you create this role then you can make SSO mandatory but always have a backdoor into the configuration in case SSO is misconfigured or the SSO certificate expires.
For a step-by-step guide on how to create an SSO Admin, see Create an SSO Admin role