Villa sacked Paul Lambert last week with the club in the relegation zone and announced Sherwood as his replacement before the FA Cup fifth round victory over Leicester City on Sunday.
The former Tottenham boss was not officially in charge for that fixture, but did give his new players a half-time team talk.
And Sherwood believes Villa need to stop playing within themselves and take the game to their opponents.
"The team looked a bit tentative against Leicester City in the FA Cup," he said as he was presented to the media on Monday. "We have to play on front foot a bit more.
"Let's have a go at fighting and start throwing a few punches ourselves."
Villa's support has dwindled in recent years, with empty seats regularly on show at Villa Park, and Sherwood is keen to win back stay-away fans.
"I haven't been a manager here yet, but when I came to play here, it was a difficult place to come and get results," he continued. "I want to turn this place back into a fortress. It's very important this club stay in the Premier League.
"None of these players want to be relegated, no-one does."
Sherwood has been linked with a number of other jobs since leaving Tottenham at the end of last season, but says he did not have to think too long about taking the reins at Villa.
"It's a fantastic opportunity and a huge football club," he added. "When I got the call to ask if I'd be interested in coming to present to Villa it was a no brainer and I said yes first and we'll negotiate afterwards."
Sherwood's first official game in charge will be at home to Stoke City on Saturday.
