For explanation about the tiles, please see our encyclopedia entry for Mahjong Tiles
Step 1:
You will always have 13+1 tiles.
So every turn you will have to discard one tile by clicking it.
On the below image, (1) - the new tile you got from the deck.
(2) - you should discard one tile from the 14 tiles (it's ok to discard the new card you just got)
Step 2:
Your Goal is to arrange the 14 tiles into one of the following sequences:
Or
Or
Or
All of your tile are from the same suit (for example all are Bamboo)
lots of other winning options exist, the four listed above are the main ones, but look for what your opponent is doing to learn more!
Step 3:
When your next opponent discards a tile that you might need, a Yellow hand will appear (1)
Click the text label below your tiles (2) to get the tile (instead of getting a new tile from the pile).
Then the tile will be added to your set, and the set will be exposed on the right side (3).
Then the board will look like that:
Step 4:
Sometimes, as explained on step3, when you will want to pick a tile that the opponent discarded (1),
a message "Click tiles(s)" will appear (4).
This is because there are more then one option to make a set,
in the example below we can create 2-3-4 set (2) or 3-4-5 set (3).
click on the tile you want the new tile to join to (for example, click on the "2" tile to create the 2-3-4 set).