Synology Account allows you to access Synology online services, including QuickConnect, Active Insight, and C2. Synology C2 Backup · Synology Active Insight · Support Ticket · DDNS
DSM and certain applications have separate login web portals. You can customize the login styles of the login screen by selecting from a variety of templates.
On a NAS that runs DSM 6, you see a (blue) screen where you can enter a user name and password. Enter your credentials and click on the Sign In button.