Syncing depends on where you have assigned your data and what service you have setup on both devices.
If you want to sync with apple calendar or reminders for example, you must have the same apple id on each device, then look in the apple calendar and reminders app that came with your device(s). You should have the same data shown on each device there. Then informant will automatically show that same data.
If you want to sync with google calendar, google task, toodledo, evernote, or informant sync you must login to the same account on both devices at informant settings>accounts and complete a sync.
Now assign your data to the service you want to sync to. For example on iOS Informant:
For events, edit an event and scroll down/tap the 'calendar' option and choose a calendar under the service you want to sync to.
For tasks, edit a task and tap the project option and choose a project assigned to the service you want to sync to.
For notes, edit a note and tap the (i) icon, then sync to, and choose the service you want to sync to.
If you still have trouble, please let me know what sync service you are trying to sync to and we can focus on that.
I also encourage you to check our Youtube channel as we have some great tutorial videos there on syncing. https://www.youtube.com/channel/UCpU7aW58LSn6pqJ4PxWzdCw/videos