How to increase primary filegroup size in sql db

Question

How to increase primary filegroup size in sql db ????
I am getting error when i tried to put nonclustered index


error---

Could not allocate a new page for database 'WMS_BATA' because of insufficient disk space in filegroup 'PRIMARY'. Create the necessary space by dropping objects in the filegroup, adding additional files to the filegroup, or setting autogrowth on for existing files in the filegroup.