Install SUMO, OmNet++ and Veins respectively.(Or Instan Veins)
SUMO is easy to install. You can follow the official github page. OmNet++ is not install-friendly. I used v5.5.1 and tried on Window, Mac, Ubuntu, even docker but I encountered different kinds of errors. Finally I installed it on Ubuntu 16.04, and it works well later, which is the ONLY platform I suggest for OmNet++ v5.5.1. Instan Veins is also recommended if you only want Veins. But I didn't use it.
Then leant some basic knowledge about SUMO (learn here) and OmNet++ (learn here) before you start Veins.
I don't think the official install instruction is good, readable. It's kind of confusing. I suggest to do it following the instructions.
./sumo-launchd.py -vv -c sumo (Refer to complete steps.)
veins-veins-5a2_dyt3_workwithRemould.zip is the back up file.