Welcome to Logseq and the community @kashif_nadeem! 
Logseq is a local tool aimed at individual users. So there’s no concept of a user and no login (unless you use Logseq Sync, but that’s also aimed at individuals and not suited for collaboration).
We recommend people use Logseq’s local apps as the browser version is a light version that’s missing support for themes and plugins. The docker build is basically what you see on demo.logseq.com (which is not meant for day-to-day usage, only to testdrive Logseq).
If you’re looking for collaboration, Logseq is currently not the tool you’ll want to use. While the devs are working on a real-time collaboration service (which will be paid), this could easily take another 12 months to complete. You’d be better off using something like Notion or Roam if you want a tool for collaboration.