Tabua said a win against Japan and Canada was "vital".
He said Fiji will have to set a good platform before its matches Australia and Wales.
"We have to start off well," Tabua said.
"It's Japan and Canada. Those two games are vital. We will not worry what's further down the line. It's what straight immediately in front of us which that is vital. I know Japan will come out firing and Canada as well.
"If we set ourselves a good platform from those two games then it leads us to the next stage which is Australia and Wales.
"So the first two games are vital for us and it's a three day turn around.
"So we have to go out there and be prepared to take the bull by its horn and go hard at it and win for Fiji."
The national side is in its fifth week of camp in Sigatoka. The team held three training sessions yesterday with the main focus on game situations.
Tabua, who took up the job as coach following the resignation of Wayne Pivac early this year, said he could not complain about the time frame given to him to build the team.
"In this fifth week of training the focus is all on game situation," Tabua said.
"Everything we are doing at training is about the game. We are breaking it down and putting them into the game situations.
"So the training varies and that's the plan for this week. The five weeks is what was given to us and this is the best we could do."
The Fiji team flies out to France on Friday.
The team will play against FC Auch Gers and Sporting Club next week as part of its final build for the RWC.
Tabua said the matches would give him a chance to polish up combinations ahead of the against Japan on September 12.
"For us this two matches will be mimicking the Wednesday and Sunday opening round pool games," Tabua said.
"We will be fielding two different teams. Then we have about two weeks before we go into match camp."
Fiji's second pool match against Canada is on September 16.
The national side takes on Australia on September 23 with the final match against Wales on September 29.
Adapted from Fijitimes Online