where should I play these bishops !!?? (opening)

Bf5 attacks weak pawn c2 but is not protected oh Lord it's complicated looool

Usually the squares on the fourth rank from your side of the board are the most standard way to develop the bishop. The fifth rank is often seen in openings but you'll have to know how to respond to a side pawn kicking away your bishop: do you take the knight (if there is one to take) or do you move back, and in which direction?

The third rank may block some of your pawns or other pieces. The second rank is often considered very passive but in some cases unavoidable if you want to develop your bishop, for example when a pawn blocks you from moving your bishop any further.

The last one is the fianchetto technique, where you move your b or g pawn and place your bishop behind it. There are many situations where this can be used, often it is inferior to placing it more in the center of the board but it can be a great weapon since many people just skip over the threat of the bishop when it is so far on the side of the board and seemingly away from the action.

thank you for your answer @Wildekaart i'll consider all this.....

You do want to develop one of your bishops to castle. Bishop to f5 controls the most squares and is easily defendable with your g pawn, your knight, or even just moving your e pawn forward and defending it with your queen. Moving either bishop right behind the queen cuts off some of its options to retreat. Having your light-squared bishop attack their knight is cute, but the knight is defended twice, so the bishop is under x-ray attack. If their knight ever finds a way to move and attack, say, your queen, your bishop is in danger of hanging. Bishop to e6 may defend the queen, but if they ever attack your queen, it's almost always moving anyways. 

Note we're talking every small differences here between some of these bishop moves, unlikely you'll ever be able to make calculations that will always get the best move within the tenths of a point. You just need a developing plan. In general, claim as many squares as you can, including any squares you deem key. Opening theory might note that certain squares have a tendency to become key, making it easier to know what to target.

You can also see common moves. In Scandis, I find the light-squared bishop often does end up attacking the knight by going to g4, but earlier, the piece tends to already be out by now. Though it's not the only option, I'd have to see the game in question to know if you chose another common alternative for sure. From what I see, this is a line black actually wins more often than not in, so I'm guessing the problem for you isn't the opening here, though again I'd have to see the game(s) in question to know for sure.

https://www.365chess.com/opening.php?m=10&n=8197&ms=e4.d5.exd5.Nf6.Nc3.Nxd5.Nxd5.Qxd5.Nf3&ns=3.20.27.45.13.13.2639.3605.8197 You can check here for some of the common options. I have it under one of the lines I saw you faced via openingtree, but you can run it through different ones.

I will say in the position you showed, bishop f5 or bishop c5 would have been my favorites for the space they take up, though the bot shows f5 as the clear winner. My guess is due to the preference of queenside castling here, or the power of something like c3 by white if you do bishop to c5, but I could be wrong. 

Great @catmaster0 thank you very much I'll try to apply all this in my future games.