Every business application has the same five surfaces: user and role administration, data (what it stores and where), integrations (what it talks to), access (how people sign in), and support (who you escalate to and under what contract). Find those five and you can administer almost anything competently within a day.
Start with the admin console and read the role list. Roles reveal how the vendor thinks about the business — clinical vs billing vs front desk, estimator vs project manager. Map the client's real people to those roles and you have both an access model and an onboarding checklist.
Then find the sign-in method. Native username and password, Single Sign-On (SSO (Single Sign-On)) via Entra ID or Google, or both? Where SSO is available on the client's licence tier, moving to it removes an entire class of password problems and makes offboarding one action instead of eleven.
Finally, record the vendor relationship: account number, support portal, contract owner, renewal date, support hours and escalation path. When the application breaks at 9am on a Monday, your value is knowing exactly who to call and with what account number.