How to manually flash your android device? Want to update my android version myself. The phone manufacturer isn't providing any updates. Is there a way to update from Jellybean to kitkat manually? 
I'm using Micromax A76 Canvas Fun. Currently on Jellybean 4.2.2
Custom ROMs (the unofficial ROMs made by the community) are usually mostly made for popular phones (there are usually more developers), so obscure OEMs like Micromax usually don't get custom ROM ports. Safest place to look for phone modding and customizing is Xda-Developers, if you find a suspicious site that claims to have ported KitKat (in this case), it's usually too good not to appear on xda, in other words, it's probably fake. 

Android ROM needs to be tailored for each specific model, you can't just, for example, go somewhere and download the universal Android update and install it on your phone.  You can always try to port CyanogenMod (the most popular custom ROM) to your device, but the process is rather complex and you'll have to learn a lot of things before you get to do such feat. 

In case you find a ROM, you'll need to have your bootloader unlocked, so that you can install custom recovery image that will let you get into recovery mode (similar to BIOS on the PC), from where you can install actual ROM files, after which the flashing process is done.