The England striker secured what he described as a “dream move” from Southampton to his boyhood club in June, shortly before heading out to the World Cup with the Three Lions.
Lambert, 32, says he wants to ensure he is in peak physical condition ahead of the opening weekend of the domestic season when the Reds take on his former club.
And he reported for duty a week earlier than those involved in the World Cup were expected back by the club, telling the Liverpool website he just could not wait to get started.
Lambert completed his move to Liverpool in June
"Probably for the first time in my career I've been looking forward to pre-season - and it's not bad for a 32-year-old to be saying that,” he said.
"I was itching to get back, be with the lads and play football. It's my second day and I'm enjoying it. It's hard, but I'm feeling good.
"I thought it was massively important I come back early, and make sure I'm in the best shape possible for when the season kicks off, because that's what all this is for."
Lambert was Brendan Rodgers’ first signing of the summer and the move represents the realisation of a lifelong ambition for the Kirkby-born striker.
He put pen to paper with the club he watched as a young boy with his father, just days before flying to Brazil where he featured against Uruguay.
Three weeks after returning from the World Cup the dream became a reality for Lambert and he admitted it is finally beginning to sink in.
He also assured fans he is focused on not only making up the numbers, but playing a key role in helping Liverpool build on the their second-place Premier League finish last season.
"Obviously it's a dream, but I do believe I should be here and there are things I want to prove," he added.
Liverpool's pre-season schedule
- 16 July: Brondby (A)
- 19 July: Preston (A)
- 24 July: Roma (H)
- 27 July: Olympiacos (H)
- 30 July: Man City (H)
- 2 August: AC Milan (H)
- 10 August: Dortmund (H)
"It's all about gearing up for the first game of the season, but I'll have a full week of training here at Melwood and then I'm looking forward to the trip to America.
"It's a lifestyle every boy dreams of – and it's at Liverpool. It's common sense that I was always going to back early – that was my intention."
Away from the pitch, Lambert also confirmed both he and his family are happily adjusting to life back on Merseyside after a number of years away.
He said: "I'm settling in very well. I'm obviously a local lad, but I haven't been here for a few years.
"It's all in place now, so I can relax and concentrate on my football."
Lambert and Liverpool have a packed pre-season to prepare for, beginning with a friendly against Danish side Brondby on Wednesday.
They then take on Preston, Roma, Olympiacos, Manchester City, AC Milan and Borussia Dortmund – before getting their league campaign under way against Lambert’s old Saints team-mates on Sunday 17 August.
