Select Your category from the list of categories available , this will enable your keyword to search only that category.
Once category is selected you can then type keywords to start revealing possible matches for your product.
The more you type the less results there will be to find your product , you simply then select one that appears from the dropdown results.
Example after selecting PS1 category , typing the word crash will reveal all names with crash under the PS1 category , so will reveal all teh crash bandicoot games as well as crast team racing and a couple of others.
Example after selecting Nintendo64 Category , typing the word mario will reveal all teh matching mario titles , things like mario kart , mario party , paper mario will all appear , typing something like ma party will reveal all the mario party games.