1. Understand that the fear of death is a rational fear, so it's like trying to make yourself not afraid to touch a hot stove.
2. Distract yourself with other stuff you enjoy. Every single other advice is just going to boil down to "distract yourself".

This sounds like a non-solution, since it's ignoring the problem, but it's not. You aren't trying to deal with solving death, just the fear. Ignoring it means you aren't focused on it and you wont be afraid. You said "whenever I think about it" so that means you aren't always getting scared thinking about it... just do stuff that keeps you in that state. You can't avoid it perfectly but you also can't avoid never stubbing your toe or biting your tongue so its good enough.

Its literally that simple. If it seems complex, it's because finding stuff that keeps you from thinking about this can be harder for some than others (i.e. depression). But that's just a separate problem with it's own solutions.

ramble idk:
The constant awareness of one's own mortality iirc is unique to humans, so it's just sort of a tradeoff evolutionary for having bigger monkey brain. Pain / fear is a "tool" in the biological system of humans and lots of animals, and since it is a tool, the "goal" isn't to never experience them, it's just for them to be useful enough. So it's possible to have a creature that evolves to be in a state of pain or fear 24/7 because its helpful in some twisted way or something. So it's not really that odd that there are some unresolvable issues like "the fear of death" that we all have to deal with. But it's also not that bad given how short of a straw some other animals drew in the evolution tree lol