Sending parameters to an added admin page

I am building a plugin.
I added an admin page called ‘eventscheduler’.
Now I need to reload it to pass some parameters (data from text fields, buttons, etc) and use them to modify the wp database.
How do I get the url of my custom page?
I tried with

but it doesn’t seem to work…
Any suggestion?
Thanks in adavnce,
Davide