The 2012 British Superbike Championship runner-up will compete for the Northern Ireland-based Tyco Suzuki team.
At the moment it's all very new and fresh and I learning more every time I go out, said the 30-year-old.
Brookes's team-mate is crowd favourite Guy Martin, who has recorded 13 podiums but never won at the TT.
A third member of the Tyco team, Japanese rider Yoshinari Matsushita , died in an accident at the event on Monday.
Brookes said: I had only just met him and to be in the same team is obviously very close to home.
We all know what we are getting involved in here.
The Sydney-born rider, who made his North West 200 debut earlier this month, said he fell in love with the Isle of Man on his first visit in 2009.
He said: I've done loads of trips over to learn the track and I've done lots of years as a spectator, but this is my first year with a leg over the bike as a competitor, so there is loads to learn.
I have wanted to race here ever since I first watched bikes come down Glencrutchery Road.
I don't have any personal expectations. I just want to see how it goes and see where we end up.
The former world Superbike round winner is widely regarded as one of the most exciting newcomers to the Isle of Man event.
The fastest in recent years was Steve Plater, who lapped at 125.80 closely followed by Simon Andrews.
Team Manager Philip Neill said: As a team with a strong background in pure road racing I suppose it was inevitable that Josh would like to have a go at the TT.
He's one of the highest-profile newcomers to come to the TT in recent years, but I know it's not a spur-of-the-moment idea. He has given it careful consideration.
We won't be expecting any miracle results and there is certainly no pressure on him. Our job is to use our experience and guide him to our best ability, but Josh is a sensible lad.
Brookes took part in a parade lap at last year's TT alongside Kevin Schwantz and MotoGP star Cal Crutchlow.