Type ctrl+G or command+G to search GST
Select GSTIN from the drop-down
Select view summary at right, for GSTR1 and GSTR3B
Click download and enter the email address where you want the excel file.
Click on the email sheet, the excel sheet will be emailed on the given Email ID.
Now, check your inbox. You must have received an excel sheet in your mailbox.
To convert this excel into JSON and file it, visit https://www.gst.gov.in/