Preferences

• Settings → Tools → Build → XeLatex
• Settings → Tools → Build → ViewPdf → Okular Unique
  • Not really sure what the unique does ("Unique Instance" control according to Okular)

Usage

Just set the Build dropdown to XeLatex and Viewer dropdown to ViewPDF.

FAQ

ERROR: The fontspec package requires either XeTex or LuaTex ....

Occurs when you try and compile with pdflatex instead of xelatex (make sure Kile is defaulting to the correct compiler).