The first thing you'll need is a test card:
https://reeddesign.co.uk/testcard.htm
What you're aiming for is to get a nice, clear, bright row of coloured boxes across the top. The next 6 boxes should run from 'pure black' on the left, to 'pure white' on the right. The same should apply to the next line, of 11 boxes, but with all of the digits (from 0 to 10) clearly visible. The final line is basically the same as that but without any distinct boxes. (i.e. with a smoooth transition from black to white).
Now, of course, comes the tricky bit, which is actually working out which buttons to press! Although there are often basic similarities in the way things that are done, each manufacturer will have their own configurations for the various buttons. So we really need the exact model number for your monitor (from the back of the set), in order that we can try to track down the manual for it.
Alternatively though, you can try to achieve your aim through the software that you use to play your DVDs. Assuming that it's VLC (which is the only media player you should be using for the job), simply go to Tools > Effects and Filters > Video Effects and click in the 'Image Adjust' box. Then you can play with the sliders to get the image you require.