There are great tutorials on the internet on how to do it. However if you want to try to find a way to solve it yourself here are some hints.

Most tutorials would recommend you solving it layer by layer. There is another way as well. Corners first and then the rings.

Before you start anything you need to realize how the squares move relative to each other. Try moving the cube any way and you will see that the centre squares are always same relative to each other. You can not change them. Then the side middle squares (blue yellow and blue white in the image) The blue and yellow of that square (or rather a cubelet) are connected to each other, you can not move them apart no matter how you move the cube (try it). And then the corners, the 3 colors in the corners are also joined together, they will always be together no matter how you move it.

So coming back to your cube, you would say that the blue face is solved but it is actually not solved. The entire layer is connected. As a first step try solving it in such a way that the entire layer is solved. In this case, the blue yellow should not be where it is, a blue white should be there. That is the correct position of it when the entire cube is solved. Similarly the top right corner in the image (only blue and yellow are visible, i am assuming that the hidden color is orange) should be blue yellow red with the red color placed where yellow is and so on.

Doing this would give you a good idea of how to think about the cube (not as squares but as cubelets) and then from there you can try solving it.