Dear Shaima, where exactly is the problem? You need to provide more specific information. Do you want to assign certain membership scores to the 90th percentile, the 75th percentile, etc., of your base variable? This you can do more straightforwardly in the spreadsheet software where you've prepared your data set (e.g, Excel), although it is also possible in fs/QCA.
In addition, you should be aware that the fs/QCA software does not return the full model space of a QCA solution. That is, you might miss some models that fit your data just as well as those models that will be presented to you by fs/QCA in its final output (for technical details of this problem, see http://erx.sagepub.com/content/38/6/487 and http://smr.sagepub.com/content/early/2015/10/22/0049124115610351.abstract).
Moreover, the manual decomposition of the prime implicant chart in the fs/QCA software will also put you at risk of missing some models.
Could you please rephrase your question again, as currently I am confused what actually you wish to examine. If you are trying to find out about the nature of the data then you should follow the instructions given above. But if you wish to make certain analysis then you have to be more specific please.