1. Go to a command prompt and enter this:
dism /online /enable-feature /featurename:NetFX3 /all /Source:d:\sources\sxs /LimitAccess
Note: Source should be the Windows installation disc. In my case, this was located on D:
2. Go down to “Specify an alternate source path” and enter “d:\sources\sxs” as the path.
Now you should see this under your Features list: