You have to attack your opponent's weak points. In the position above I would double the rooks on the 7th file, attacking the b7 pawn. (or on the 6th attacking the b6). You have to go after pawns and put your pieces on their optimal squares. In the position you show, your rooks are uncoordinated and the bishop is not doing much. You have to play actively. Otherwise your extra material is not going to help.
Position with piece advantage but no plan.
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You can't make a general rule for "positions like these". Each position has it's own characteristics. For example, in the position you give above, you have a mating attack! 1. Ree8 threatens 2. Ra8 mate. If Black responds with 1...b5 (to give his king an escape square), you play 2. Ba5 (blocking the escape and threatening 3. Ra8 mate again. If 2...b6 3. Ra8+ Kb7 4. Rfb8+ Kc7 or c6 5. Bxb6 and you keep chgasing the king. The White king will be safe on b2. Don't even look at your pawn on h3! It is completely irrelevant in this position. Play for mate!
Read my article "It's Never Too Late for Mate" http://www.chess.com/article/view/its-never-too-late-for-mate
and
http://www.chess.com/article/view/its-never-too-late-for-mate-part-2
Sometimes when I play I manage to win a piece early on in the game. But I am not able to convert this to my advantage if opponent is not exchanging material. This has been happening to me for quite sometime. I just dont know how to progress. I get stuck and blunder or lose the advantage. Example today I was playing OTB 2 vs 2, it was a beer match and I reached this position but couldn't force a win. I couldn't finish the match as we were playing for quite a few hours and my mom called me but my partner blundered the bishop and lost the game.
So how do you continue in matches like these
1) secure the king from checks first?
2) go after pawns?
3) try to exchange material?
4) find mating pattern?