Can someone guide me how to customize admin schema for multi vendor e-commerce

Questions and Answers Strapi Backend
1
System Information
  • Strapi Version: v4.25.8
  • Operating System: window
  • Database: postgres
  • Node Version: v18.20.4
  • NPM Version: 10.8.2

I’m working on project multi vendor e-commerce. And newbie with strapi.
I want extending the existing schema by adding company name field. From this requirement I also need to custom auth page for add company name input to each vendor. It means each company can have multi admin.