You should first become familiar with the new features of UD6 1.03 and the upgrade path that is best for you.
Run the UD6 1.03 installer executable, and when prompted for an installation directory choose the directory where you have Uniface installed (eg:
If you were using the evaluation version of UD6 1.02.23 then the DLL's were named
mhgfp140x.dll. Because new UD6 1.03 evaluation DLL's are named
mhgfp140.dll you will have to change the names referenced in your INI file, and you should DELETE the previous DLL's.
USYS$UD6_PARAMS in your ASN file as described in the ASN Settings for Upgrading guide and the What's new in UD6 1.03 guide.