Positioning is primarily a marketing term. It simply means where to position yourself in the mind of your audience relative to your competitors. Think of it as a graph with 4 quadrants, and you are positioned at one spot in the graph in one of the 4 quadrants. To make this easier to understand, consider the following classical illustration of how some car brands are positioned with regards to price vs. quality:
You have different car brands on the graph. The more you go to the right, the higher the quality. The more you go up, the higher the price. So obviously, the best position would be in the lower right corner because a car of very high quality and very low price offers the best value to the customer.
Similarly, you can use positioning to determine where to position yourself in the dating scene relative to your competitors. There are some differences, however. You always have to appear at maximum value to the women who interest you. Therefore, having high and low values on your axes does not work. So this is what you can do. Consider one offering that you are making. What you need are 4 opposing manifestations of that offering as exhibited by your competitors. These manifestations go on your graph. For instance, let's say wealth is your offering. Wealth can manifests itself as luxury. Opposite to luxury you have modesty. Similarly, wealth can also manifest as adventure. Something opposite to that is hard work. So now you can label your graph with modesty and luxury on one axis, vs. hard work and adventure on the other axis. It is important that all 4 manifestations have value. So, even though "hard work" may seem unpleasant, there are many people who value and respect someone who is hard working.
From the graph, it is easy to see that you can avoid most of the competition and stand out if you position yourself as both adventurous and luxurious. You would be appealing to the women who appreciate both of these qualities in a wealthy man, and you don't have many other men who are similarly valuable to these women. Again though, I will stress that this is just a simple example. In reality, you have to be more creative than this and do a lot of research into who your competitors are and what they are doing.
Done properly, the graph will give you a good idea about the positions that are least competitive. In the very least, you will learn from the graph what your competitors are doing to appeal to the specific segment of women, and what you can do differently to distinguish yourself from them.
But positioning is more than simply choosing a place on a graph. It is always the value to the women that is most important. So you need to recognize what value you are offering women, and how it is different from and better than the offerings of the competitors. You need to realize which aspects of your offering are most important in creating value. That enables you to appeal to them to the best of your ability.