Use the account for your organization. The first time you sign in on this browser, you will create a device PIN so you can unlock the installed app without internet (your PIN stays on this device only).
Offline: after you sign in, open Dashboard and each section you use (e.g. Clerking) once while online, then install from Settings. See Settings → Offline & device for the full checklist.
No account? Register your organization
Invited by a teammate? Open the join link your admin copied from Settings (don't use "Register your organization").