Do you already have a single sign-on (SSO) identity provider? You can set up a SAML or OpenID Connect (OIDC) integration to allow your readers to log in using those same credentials. Set up either one in Security and access > Access & SSO, in the Login methods card.
Review the configuration options available at Single Sign-On (SSO). For OpenID Connect, including ClassLink, start with OpenID Connect (OIDC) SSO overview.