You'll have to extract the public.zip file's contents into the 'public' directory.
Then what you could do is use one of the existing Wells as a guide. Find this actor file:
\binaries\data\mods\public\art\actors\props\special\eyecandy\well_1_a.xml
Create a duplicate of it in the same folder and name it 'well_2_a.xml'
Within that file you'll see this code:
<variant frequency="100" name="Base">
<mesh>props/wrld_well_a.dae</mesh>
<props>
<prop actor="props/special/eyecandy/well_woodbit.xml" attachpoint="woodbit"/>
</props>
<texture>props/wrld_well_a_1.dds</texture>
</variant>
In the code are the collada and texture files that the existing Well uses. Change those references to point to your files, which should be placed into -
model: binaries\data\mods\public\art\meshes\props
texture: binaries\data\mods\public\art\textures\skins\props
The texture file can be either dds or png format, and the model a 'clean' collada file (see more info
here)
You can remove the following lines from the actor file:
<props>
<prop actor="props/special/eyecandy/well_woodbit.xml" attachpoint="woodbit"/>
</props>
This references another model which your Water Well won't need.
In Atlas, you will then find your Well by putting 'well' into the filter and choosing the 'Actors: (all)' option: