You can access Covidence using your Archie credentials. This will establish an account under the email you use for Archie; thus if you previously created a Covidence account using that email, logging in with Archie will lead you to the same account.
There is not currently a way to link multiple accounts, such as a private email with an Archie credential log-in.
To log in with Archie, click the purple "Sign in with Archie" button. Enter your email and Archie password. Accept the permissions (shown below), and you'll be ready to go!