Curiously, 3.73 is not the final Vita firmware—3.74 is. However, 3.73 holds a unique place in Vita history. It was the version that forced the hacking community to innovate.
Use a USB cable to connect your Vita to a PS3. On the Vita, select Update by Connecting to a PS3 system . Manual Installation via USB (PSTV Only) Ps Vita Firmware 3.73 Download
For PlayStation TV users, you can perform a manual update using a USB flash drive. Curiously, 3