Copy the x86/kea.dll to C:\Program Files\Hexagon\ERDAS IMAGINE 2015\usr\lib\Win32Release\rasterformats

If you have 64 bit Imagine installed, also copy x64/kea.dll to C:\Program Files\Hexagon\ERDAS IMAGINE 2015\usr\lib\x64URelease\rasterformats

Run File->Configuration->"Reconfigure Raster Formats".

and restart Imagine.
