When you install a synchronizer on a structure, you make this structure automatically sync with something else. For example, after you have installed and enabled a Links Synchronizer, any changes someone makes to the structure will cause issue links to be created or deleted to match those changes. Or when you have installed and enabled Filter Synchronizer in Add mode, creating or changing an issue that causes it to pass the selected saved filter will cause this issue to be added to the structure.
When you install a synchronizer, you define its parameters. Those parameters can be edited later.
Please note that after a synchronizer is installed, it's not working yet - it must be Enabled to start monitoring the changes.
To install a new synchronizer:
Find the structure you'd like to sync. The Sync With column shows currently installed synchronizers. Click on the Settings link in that column.
If you don't see Settings link in the Sync With column, then you possibly don't have Control permissions on this structure.
Enter synchronization parameters. Each synchronizer has its own parameters, please refer to the specific synchronizer documentation.
If you're not acquainted with how this synchronizer works, please make sure to read the Rules section at the top of the page. Especially text in red.
Import and Export are actually a one-time Resync. Export is resync from Structure and import is resync into Structure. If you need to run export or import periodically, you can set up a synchronizer with all the parameters but without enabling it - so no synchronization happens in the background. When you need to export or import, you can open Synchronization Settings page for the structure and run Resync. Just make sure you've selected the correct Resync direction!