Unity Editor does not working For multiplayer

I don't know anything about programming , hence i downloaded youtube user's ONEMANARMY the multiplayer game for unity. so i opened it in unity with out any problem but when i hit play button it freez. in TASKMANAGER if i start the unity in 250mb memory and it step by step keep increasing the memory . but doesn't respond . Even i keep this thing on for 30 minutes but it didn't worked well.
Please guys i need help quickly my crew is waiting for me.