Hey Tomas - welcome to the Core ! 🙂
The Wind deformer is rather unique among deformers in that it doesn't have much in the way of visual feedback, so it can be tricky to see which way up it is unless it is assigned to a flat plane, where it is a lot easier to see the direction of movement than it would be were it applied initially to something round or solid !
Start a new scene, so that you can understand how it works. Add a plane object with default 10 x 10 segments but make it +Z.
Now add a Wind Deformer to the scene, which by default is 'waving' down the X axis, which would be 'along' your Z facing plane, and therefore correct orientation, so if you drag the wind under the plane and give it some strength (amplitude) you should see the plane move properly. If you are using flag mode, then you would additionally move the deformer relative to the object, down to one end of it.
Once you can visualise how it is working you should be able to align it correctly with the actual object you want to bend. So, once you have selected the wind, use Quantized rotation (hold shift once you start rotating to snap to quantize value) to rotate it exactly 90 degrees from where it is so that its X direction is pointing in the direction you want the wind to move through the object. If you are still stuck, upload the scene file, and we can do it for you.
CBR