Apply filter:

If your filter create raster:

<use filter="url(#MyFilter)" x='0' y='0'/>

If you will use filter effect to fill a shape, you have to define pattern in <defs>:

<pattern id="motif" patternUnits="userSpaceOnUse" x="0" y="0" width="400" height="400">
<use filter="url(#MyFilter)"/>
</pattern> 

and use this pattern to fill:

<circle cx='200' cy='200' r='200' style='stroke:black;fill:url(#motif)'/>