best thing if you don't know how to do it is get a haynes manual, its better than asking the forum because you can have it with you by the car.
but i have taken a million micra bumpers off and its all pretty straight forward, the back ones you can see whats holding it on if you just look around the edges of it, except for the two secret bolts on the inside of the boot,
the front one again most of the bolts you can see by looking at it, but yes you have to take the grill and headlights out to remove it.