Can't access my Windows 10 laptop frim my iMac

I want to share files between my iMac and a Windows 10 laptop. I have been able to get the laptop to see the iMac, but nothing I have done so far has worked the other way around. The iMac will not access the laptop. Please help with some advice. Using OSX El Capitan and Norton Security for the Mac. Also using Norton on the PC.

Thanks,

Jim