Is it possible to artificially create a star

We know that Jupiter's a gas giant. Suppose if we take very powerful nuclear weapons and shoot them on the atmosphere of Jupiter, so that it initiates nuclear reactions there, will it slowly turn into a star?

No, sorry. It is not possible.

First, Jupiter is a hundred times too small in mass to sustain nuclear fusion.
Another problem, our nuclear weapons are far, far too weak to affect Jupiter in any way.
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It makes a good story, though. Jupiter became a star in the movie, "2010 The Year We Make Contact" based on a book by Arthur C. Clarke.
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I've heard speculation related to that, but any nuclear reactions would have to take place near Jupiter's core, where the pressure might be high enough to begin a temporary ignition of hydrogen fusion. I don't know how valid this is, but some people were worried that when the Galileo probe was de-orbited into Jupiter, the plutonium used in its thermoelectric generator would sink to Jupiter's core and detonate, causing a chain reaction. Jupiter would briefly flare up, destroying earth's atmosphere in the process. Obviously that never happened. Likely, however, the plutonium was vaporized by the probe's entry into the atmosphere.

I think it was in the book "Blue Mars" as well that the author discussed the possibility of temporarily igniting Jupiter. But again, I'm referring only to speculation, not fact.

No, not yet. Jupiter has only 8% of the minimum mass necessary to create enough pressure for nuclear fusion ignition to even start. Where are you going to get all the additional mass from, AND WHY? "...Your facts are [still] uncoordinated and your thinking is illogical..."

Yes by adding mass

No.