[galaxy-user] using SnpEff and SNPSift in Galaxy

I have a VCF file and I want to filter it for nonsynonymous/ deletion/ insertion seq variations. Once I filter this file and compare between tumor vs normal samples and then annotate such variations. I believe I can filter this file using SnpSift and then can annotate with SnpEff, When I try to use Snsift filter it just says arbitrary expression. Are there rules how to use expression for a particular filter with in galaxy. If any one has used SnpSift in galaxy may share their expertise. Thanks Kanwar