Kamil Zydek, 34, denies being part of a team of three men who planned the killing of Mr Stolarek, 41, and then the disposal of his body.
The body of Mr Stolarek, a Polish national, was found by a service engineer at the Chain Bridge Road pumping station in Boston on January 12, 2020.
A jury at Lincoln Crown Court heard police launched a major police investigation and two other men, Lukasz Ferenc and Adam Kaminski, have already been convicted of Mr Stolarek's murder.
Also present when Mr Stolarek's body was driven away was Artur Klosowski, who later fled to Ireland in a Vauxhall Astra which had "blood stains" in its boot, the jury had heard.
The prosecution allege Zydek was working in a team with Ferenc and Kaminski when Mr Stolarek was attacked and disposed of during the early hours of November 28, 2019.
Gordon Aspden KC, prosecuting, told the jury Mr Stolarek was tied up and savagely beaten at the home of Kaminski in Union Court, Boston.
Mr Aspden alleged Mr Stolarek was then put in the boot of a Vauxhall Astra car driven by Artur Klosowski, with Ferenc and Zydek helping to dispose of his body.
Giving evidence via a Polish interpreter, Zydek admitted he was a passenger in Klosowski's car when it was driven eastbound across Boston's Sluice Bridge towards Union Court at 3.46am on November 28, 2019.
ANPR cameras showed it travelling back in the opposite direction 15 minutes later.
Answering questions from defence barrister, Alisdair Williams KC, Zydek said the vehicle was directed to the back of the house by Adam Kaminski.
The jury heard Zydek had been in contact with Ferenc by text message and phone after crossing over Sluice Bridge.
Zydek was asked by Mr Williams: "What was going on?"
He replied: "I don't know, I don't remember," adding that he must have been telling him that they were on their way.
Once at Union Court, Zydek said he got out of the car and went to the back door.
"I was stood in the doorway when I saw what they were doing," Zydek told the jury.
Zydek said he didn't know what to do, and went back and forth to the car.
"I went in, I went out," Zydek added. "I didn't even see his (Marcin's) face."
Zydek said Klosowski then got back into the car.
"When Artur was getting back in the car, Adam and Lukasz were putting Marcin in the boot," Zydek told the jury.
"I didn't know what to think. I was scared. Everything was happening so quickly."
Zydek said Ferenc then also got in the vehicle.
"I said to Artur to go to a hospital, but Lukasz disagreed," Zydek insisted.
"I said to Artur that if you can't go to the hospital then leave him in front of the hospital, but Lukasz got angry and told me to 'shut up.' "
Zydek was then asked what condition he thought Mr Stolarek was in?
He replied: "I don't know, I have no idea."
Zydek said Ferenc then gave Artur directions where to drive.
The jury heard Artur Klosowski left England in January 2020, driving the Astra car to Holyhead in Wales before taking a ferry to the Republic of Ireland.
Artur Klosowski, previously of Witham Place, Boston, who was arrested in the Republic of Ireland and brought back to the UK, was jailed for 28 months in July 2021 after he admitted conspiring to pervert the course of justice by driving the car involved in the murder.
Zydek was arrested by Dutch police earlier this year and extradited to the UK to stand trial.
The trial continues.