No, Carolyn, I'm sorry but you can't.
You can't upload a DNA raw data file here. What you can do is to enter YOUR OWN DNA results on YOUR OWN profile. I emphasize the "your own" because WikiTree's policy - for privacy protection purposes - is that you are not permitted to enter any DNA information for any living person other than yourself.
Most deceased persons never took a DNA test, since they're so recent, so it is not likely that any of them have DNA results that could be entered. If your brother-in-law's ancestor is one of these rare exceptions and you know the place where the test was done and his kit number there, then I recommend that you write to info @ wikitree.com (without spaces) and ask them about entering it.