Using 2D Point Shapefile as Starting Particle Locations

How can 2D Point Shapefile be used to assign starting particle locations on a Slice?

I am using FEFLOW 6.2 and/or 7.0 to run a 3D transient model. I have a 2D Point Shapefile. Horizontally, these points spatially do not coincide with computational nodes of the mesh; they are generally located within mesh triangles.
I want to use these locations as starting points for particle tracking. Repeated particle tracking runs, so the starting locations will be the same. I want to start particles on a selected Slice, then repeat on another Slice, etc.
This would be much more convenient than generating several sets of 3D Point Shapefiles.

Particle-tracking techniques start at mesh nodes. Accordingly, you need to use a nodal selection. If the locations of the point shapefile do not coincide with mesh nodes you can simply use a snapping distance.