Hi Akash, if you bought the game on Steam, then it should update automatically. If it isn't updating automatically, open up the game properties (right click the game in your Library) go to the "Local Files" tab, then select "Verify Integrity of Game Cache" it should force an update if one is available.
SOURCE: https://gaming.stackexchange.com/questions/127901/is-there-a-way-to-manually-upd...