Austria are level on focuses with NI in runner up, which gets a play-off for the following summer's competition.
The sides attracted 2-2 Belfast in October and the victors will be in an ideal situation to advance.
"It's sink or swim - there are so many words you can utilize, however we must win," said Shiels.
With Britain five focuses clear at the top with four games left, Northern Ireland and Austria look set to fight it out for the play-off spot for the competition in Australia and New Zealand.
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October's emotional attract Belfast saw Austria hit a physical issue time balancer.
The two sides actually need to play Britain, who travel to Windsor Park on Tuesday, and afterward face lower-positioned resistance in their last games.
"This is the World Cup, the greatest competition on the planet. We know if we somehow managed to beat Austria the possibilities meeting all requirements for the end of the season games as other participants - we would be chances on, yet that is thinking excessively far ahead," added Shiels.
"We need to consider the here and the at this point. Everything rotates around beating Austria. Drawing would be acceptable however that is about it."
We need to take our risks
Since the October apparatus, 22 of Northern Ireland's homegrown based players have entered full-time preparing for this mid year's European Title, where Shiels' side will again confront Britain and Austria, alongside a Norway who will have striker Ada Hegerberg accessible after she finished her worldwide exile.
Shiels, who has been in control beginning around 2019, feels his players have grown intellectually as well as actually from their change to impressive skill.
He added: "It is tied in with estimating the brain science of the game. It is tied in with telling players that there will be times of the game where we will be against the divider.
"There will be periods where we can counter-go after with a few energy and there will be periods where we will have some tension on them.
"Those articles occurred in Belfast, that is the means by which the game ebbed and streamed. Whenever we get an opportunity we need to take it."
Shiels added match arrangements have included going into the "best conceivable detail" to manage an Austrian crew loaded up with ability, including Hoffenheim forward Nicole Billa who has 41 objectives in 76 covers.
"The players have given a great deal this week as we plan for the game and some of the time you need to ask what more would we be able to do?" he said.
"At the point when you are playing a group like Austria you must have bunches of things at your disposal.
"There are bunches of individual characteristics that they have. Six of them played in the Bosses Association just last week.
"That is the assignment we face, assuming we check the comparatives out."
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