In Candy Crush Saga level 490 you need to clear the jelly and score 30,000 points to complete the level. Initially you will not be able to see the jelly as it is hidden under the chocolate at the bottom of the board. Although there is no chocolate maker, there are bomb makers that produce 10 move bombs at the top of every column at the bottom of the board so you need to destroy these quickly and you have just 45 moves to win.
Start level 490 by making special candies. You will need vertical striped or striped and wrapped combinations to remove the most jelly but as soon as you do bombs will drop. Although chocolate will probably grow back over them in the early stages of the game, so they are unlikely to go off, it does make it tricky to start clearing that area of the board. That is why it is good to have a lot of special candies available before you activate any. The best special candies to use are a color bomb and striped, wrapped and wrapped or stripe and wrapped. You can usually ignore the bombs and work on the jelly, although there may be one bomb that refuses to disappear and you will need to match it.
There are quite a few boosters that can be used on level 490. The most useful is probably a lollipop hammer to take out an annoying bomb and possibly some extra moves if you have some from friends.