Speaking to TNT Sports on Tuesday, Mikel Arteta said: "We really had to dig in to find the magic moment at the end.
"We're starting to create an unbelievable energy in the stadium, we were all pushing to get it done and together we have done it.
"You're very nervous [watching a penalty shootout], hoping for the best but you know it's a bit of a lottery. We had prepared the day before.
"So credit to the goalkeeping coaches and everyone that has contributed. It's really difficult to play against Porto, they are really competitive."
Arsenal are through to the Champions League quarter-finals for the first time since 2016 after beating Porto on penalties at home on Monday.
The Gunners head into the first international break of the year sitting in first place of the Premier League table, a testament to Arteta's work at the club.
