The former Yeovil Town and Bristol City manager was appointed at Whaddon Road until the end of the season on Monday and has been tasked with keeping the side in League Two.
A run of just one win in 15 has seen Cheltenham drop to the foot of the table, two points from safety, and Johnson concedes it is not a position he is familiar with.
"It's a very unusual situation," he told the club's official website. "Everybody starts with a clean sheet and I've got to pick the best team to win the next football match.
"The players have to understand how important it is, we have to make sure it matters to them.
"We are at the business end now and this is seven play-off games and you have to treat it as such and every game you have to go out to win."
Cheltenham's hosts York are just three points clear of danger themselves, but will be buoyant after last week's 4-1 thrashing of Mansfield Town.
In contrast to Cheltenham, Hartlepool United have suddenly found form, winning four on the bounce to climb out of the relegation zone after previously looking doomed.
They visit play-off contenders Newport County, while second-from-bottom Tranmere Rovers are at Stevenage and Carlisle United, two places and three points clear of the drop zone, are at home to Portsmouth.
At the right end of the table, leaders Burton Albion visit Plymouth Argyle, while their nearest challengers Shrewsbury Town and Wycombe Wanderers welcome Dagenham and Redbridge and Oxford United respectively.
Bury will hope to keep their automatic promotion hopes alive when they go to Cambridge United, while Southend United host Mansfield.
Elsewhere, AFC Wimbledon take on Northampton Town, Morecambe host Accrington Stanley and Luton Town look to end a six-match losing run - which has seen them drop out of the top seven - when they meet Exeter City.
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