What is it?
A small tutorial how to get Cyanogenmod 13 (Android 6.0) on a Samsung Galaxy S3.
The steps taken were described at https://wiki.cyanogenmod.org/w/Install_CM_for_i9300
Steps to perform
Boot the phone normally and upload the cm13.zip package to the internal storage. I used cm-13.0-20160110-NIGHTLY-i9300.zip from https://download.cyanogenmod.org/?device=i9300
Browse to the S3’s internal storage
Paste the downloaded zip file to the root of the internal storage
Boot the phone in download mode. Hold Home, Volume Down & Power.
Download and extract Meimdall Suite from http://glassechidna.com.au/heimdall/#downloads
In the Heimdall folder, put the recovery.img file (I got it from https://dl.twrp.me/i9300/twrp-126.96.36.199-i9300.img)
From the Heimdall folder, execute the following command
Boot the phone in recovery mode. Hold Home, Volume Up & Power. 1. Choose Wipe data/factory reset 2. Apply update Browse to internal and than the 0 folder to select the cm13.zip file
Sit back and relax while Cyanogenmod 13 will be installed