can't find administration page or instructions after installation

If you visit http://example.com/admin/by-module do you see any links for it? You should find one that points to the access control for the module which is at http://example.com/admin/user/access#module-scheduler. That is the only place where scheduler has an administration page. Other than that, it just inserts itself into the node/add and node/edit pages for users who have the permission.

I had this problem too. The solution is obvious with hindsight (you have to turn it on for each content type before it will appear for a specific node), but the documentation could be clearer...

Go to Administer, Content Management, Content Types. Edit the content type you want to use Scheduler with, then scroll through the options. Under the Default Comment Setting section, you'll see the options added by the module. You can then turn them on/off for that content type. Of course, the option will only appear to content authors who have the permission to use the module.

Steps 3 to 5 from the README.txt file:-

3. Grant users the permission "schedule (un)publishing of nodes" so they can
set when the nodes they create are to be (un)published.

4. Visit admin > settings > content-types and click on any node type and
check the box "enable scheduled (un)publishing" for this node type

5. Repeat for all node types that you want scheduled publishing for