I guess there are really only 2 methods, should you even wish to attempt something so foolhardy :-)
- If you removed a lot of the stars hydrogen, this would invoke the core to collapse and start helium carbon fusion earlier.
- By adding a hell of a lot of hydrogen to the star, you could increase the pressure on the core, causing the star to use up it's supply of hydrogen faster than it would before. Thus invoking the supernova early.
How you would do this, or even how you would get there is anyones guess - let alone why?.
