Selected vertices to measure geodesic distance to, but getting error

[srilakshmip03]

Hi, I'm very new to using MeshLab. For my project, I have 2 point clouds that I used Poisson reconstruction to form a watertight mesh from.

I'm trying to color one mesh based on how far its surface is from another registered mesh. I used the "Select Vertices" tool to select all vertices in my first mesh. I then selected my second mesh in the sidebar, and I ran the filter "Colorize by geodesic distance from the given points". I get the error

Warning: no vertices are selected! aborting geodesic computation.

Applied filter Colorize by geodesic distance from the selected points in 11 msec 

How do I get this filter to work?