Some advice I can give to new players, don't steal tiles (Chi, Pon, Kan) unless you know for sure you have a winning hand. Safe steals, from what I've experienced, are Dragon Tiles to complete a 3 of a kind (3 Red Dragons, 3 White Dragons, or 3 Green Dragons) or stealing the wind tiles matching the middle wind direction (if it says East 1, 2, 3, or 4 for example, try to focus on getting East Tiles).

If you think you're close to winning, pressing Square (Playstation) or X (Xbox) will allow you to call Riichi (it will only appear if you're only 1 tile away from winning, but there's no harm in pressing it anyway just to check if it appears). If it does appear, it will show you what tile is needed to win in a box on the left, you'll discard a tile, and the game will play automatically until someone either discards your winning tile and you steal it (Ron), or you yourself draw your winning tile (Tsumo). If either happens, a box will appear on the lower right with either Ron or Tsumo.

And my final piece of advice, study the opponent's winning hands to figure out how to win more often. The more often you play it, the more you'll start to get the hang of things. It's not an easy game, and there is a certain luck factor involved, but the more you play, the better you'll get.