From iManager you can choose the option to install products.
On that page there is the choice:

Installing Products Remotely

To do a post-installation of products remotely, use the Remote Product
Install utility

When I click on the link for the Remote Product Install utility, a
prompt for the Netware 6.5 CD1 (OS) appears.

The server is running Netware 6.5 SP5, so I have uploaded the
nw65ossp5.iso and nw65prodsp5.iso to a directory on the server.

When I enter the path to the iso, it is not accepted as a valid image.
Also, choosing the image on my local drive does not work.

It appears you have to use the default nw65os.iso, without service
packs. That is strange, as this particular server was installed from
Netware 6.5 SP4 (OES) media.

Has anyone used this Remote Product Install utility succesfully with
patched media?

Kind regards,