If you re-install IMPORT|IT on the same computer your schemas will remain. However, if you deinstall IMPORT|IT on your computer and then install it on a different computer, they will not be there anymore.
The complete configuration of a schema includes the following steps:
1. Naming the schema and Act! database connection
2. Source file type and source file directory, schema type
3. Further settings (different for every schema type)
To get to the settings of the IMPORT|IT schemas go to the navigation bar and click on IMPORT|IT Schemas under IMPORT|IT. In the main window you should now see this:

Now click on New Schema. You will be directed to the following window:

In the main window you can configure your IMPORT|IT schema.
You find the next step in the chapter Naming the schema and Act! database connection.