The Royals remain winless in three league fixtures this term following their 2-1 home defeat at the hands of new leaders Brockenhurst.
Carter conceded his side's poor first half showing left them with no complaints as they came away from the game with nothing.
But he reiterated there is more than enough quality within his squad to start climbing the table in the coming weeks.
And he believes for many of his players who were playing at Southern League level, they are still adapting to life in the Wessex League.
Carter: ‘We’ve got the squad there, it’s just going to take a little bit longer than everyone would hoped to gel.
‘It’s getting used to it, getting used to the level of football, you’ve got lads who are willing to run and run at this level.
‘It’s getting used to the change, it’s going to take time, Rome wasn’t built in a day.
‘It’s disappointing at the moment because morale and confidence is low so we need that win to push on from there, really.’
Carter cursed some sloppy defending as Brockenhurst netted either side of the break to open up a two-goal advantage.
Lee Wort pulled one back for the Royals with 20 minutes left to get back in it, although they could not find a leveller.
Yet, even if Portchester had come away with at least a point, Carter admitted it would have been unjust.
He said: ‘We weren’t good enough first half, we didn’t play well enough, we gave away a sloppy goal on 44 minutes.
‘Neither team really created any chances first half apart from we gave the ball to them and the lad finished it well, to be fair to him.
‘It was more or less from our mistake and it was the same with the second goal as well.
‘We have ourselves a mountain to climb but it sort of kicked us into life a bit, really.
‘We dominated the game from then, Worty has obviously scored, then their keeper has pulled off two or three great saves to keep them in it. On our first-half performance we got what we deserved yesterday, which was nothing.’