Ahead of the visit of the Royals, Forest had not scored in four matches in the Championship, but Lee Tomlin's late equaliser ensured that the East Midlands outfit registered just their second point from their last five games.
Karanka remains with just one win from his eight matches in charge - away to leaders Wolverhampton Wanderers - but the Spaniard was delighted with his team's second-half display at the City Ground on Tuesday night.
The 44-year-old told BBC Radio Nottingham: "We need to go to the pitch in the way we've gone in the second half because in the second half the atmosphere was amazing and we need to give the crowd that atmosphere.
"We needed to be more aggressive because we were losing every single challenge in the first half. I'm really pleased with the response of the crowd.
"We have a lot of good players and main thing is to create those chances, to play intense, to play aggressive and if we play that way we will have chances and we will win the games."
Forest currently sit in 17th place in the league table, eight points above the relegation zone.