The basic idea to playing Minesweeper is that you attempt to find dangerous objects in a grid.  Lets call those Dangerous Objects "Gems"

The grid is completely filled with unknown squares.  Some contain empty space, and some contain Gems.  Your goal is to reveal all the empty space without hitting a Gem.

To help you solve this puzzle, Numbers in squares next to unrevealed squares will indicate how many gems are adjacent to it. 

If a empty square has a 2 in it, there are 2 gems next to it.

To clear a space you believe doesn't contain a gem, click on that square with the left mouse button.   Click using your RIGHT mouse button any square you are sure contains a gem.  

If you clear the whole grid correctly, you'll win. There you have it, the rules for classic Minesweeper.

TIPS:

Look for green "1"s that only have 1 uncovered square and no other Gems adjacent to it.  That square HAS to be a Gem. 

If you have marked all the gems that pertain to a adjacent number, click on the number to clear the remaining uncleared squares.