Step 1: Open Settings panel.
Step 2: Select "Business settings" under Global Settings.
Step 3: Click on "Add new business units" icon to add a new GSTIN/BRANCH.
Step 4: If you want to add a new GSTIN then select "Add new GSTINs" icon else select "Add branches for existing GSTINs" if you want to add a BRANCH.
Step 5: Add the GSTIN number. The display name will be fetched automatically. You can edit it if you wish so. You are given the option to add NIC username and password although that's not mandatory here. However, it is advised to fill that info here itself rather than taking the trouble to fill it in the "NIC credentials " tab. Click on save once completed.