You haven't installed ISE - only the EDK - so when the EDK looks for ISE it doesn't find it.Solution - go to the Xilinx download site an download ISE. Do yourself a favour and get 14.7 - it's still buggy, but has fewer bugs. Note that if you are on windows 10, ISE won't run at all, and you need to use the Virtualbox image (it's free, if slow) that installs an ubuntu VM with everything you need. This is also on the Xilinx download page.It's important to make sure versions line up - if you have an older EDK, it won't play nicely with newer ISE, which is one of the useful bits of loading the entire thing as a VM - everything matches. Be aware too that you need 14.7 for spartan 6 and earlier, but after that (7 series and up), you need Vivado (ISE equivalent) and Vitis (EDK), and that to install those, the complete installer is found by installing VITIS with the 'install Vivado' option.
Xilinx ISE 9.2 system requirements The documentation below shows the minimum and recommended requirements for running Xilinx ISE. If the system does not meet the minimum requirements, the ISE system may not function reliably. If your system meets the minimum requirements, it is recommended that the minimum configuration listed below be used.