The whole process depends on the phone type. If it's a smartphone, updates can be applied to your operating system through OTA (Over The Air). Simply connect to a WiFi network, then access the Settings > About. This works for most smartphones (regardless of their operating system installed).
For other phones, you will need the PC Suite application. Use the model of you phone and the brand then paste this information on Google. Download the PC Suite, connect the phone and then follow the instructions from the application.