Keep your mango on the counter until it is ripe.
The colour may change depending on the variety. However it should become soft to the touch and smell sweet at the stem when ripe.
How to prepare
With a knife to the base of the mango peel the skin off (cut away from you).
Once peeled, slice horizontally on either side of the pit in the middle to remove the flesh. Cut in to slices.
Once you are finished with the pit, clean it and try to plant the seed. In 7 years you may have some fruit (this is how long it actually takes for a stone to eventually grow a fruit!). ????