After purchase, you can right-click and "Save as" the file to your hard drive. This is the solution available.
Note: For the best experience, use official streaming services which offer offline "WORK" download modes for premium subscribers. Oru Varthai Sonnal Pothum - JioSaavn
For the best audio quality and to support the artists, you can stream or download "Nee Oru Varthai Sonnal Pothum" on these official platforms: