Just to consolidate a bit entering this will install and start running the miner in one entry:
sudo apt-get update && sudo apt-get install p7zip-full && wget https://github.com/gapcoin/GapMiner/releases/download/rev3/gapminer-linux-rev3.zip && 7z x gapminer-linux-rev3.zip && 64/gapminer -o http://mine3.gap.nonce-pool.com -p 4200 -u user.worker -x pwd -t 8