Preparing to upgrade from 11.x to 12.1.2 - fileconnect files

I swear I've looked in many docs on this website, unpacked the downloads and looked, but nowhere can I find what to do with the 12.1.2 download files to start the upgrade. There are apparently 3 relevant self-extracting zipped files:

Symantec_Endpoint_Protection_12.1.2_Part1_Installation_EN

Symantec_Endpoint_Protection_12.1.2_Part2_Tools_EN

Symantec_Endpoint_Protection_12.1.2_SEPM_EN

The Part1_Installation and the last SEPM_EN both have setup.exe executables, but they don't say which is run first. Should all three be extracted into the same tmp folder? 

How should I extract the above files (into same folder?) and which is run first?