Login into your OnSync account and click "Schedule".
Here you will get all your sessions which were created with your admin account.
In this section you will get options to sort the session list as per your convenience i.e. "Current", "History", "By anyone", "By me" and "By others".
Once you have sorted this list, you can view all your previous sessions here.
You need to check the boxes in front of the sessions, so that the session gets selected.
Now, click on the "Actions" dropdown box above the check boxes, you will get two options 'Edit' and 'Delete'.
As you want to delete the session, click on 'Delete', it will delete the selected session from your account.
To delete only a particular session, place the cursor on the specific session.
You will see a small 'x' icon besides the "pencil icon", please click on it to delete the session.
You will be prompted to confirm the deletion.