The Horaro Schedule Import panel is part of the nodecg-speedcontrol bundle and has not had any modifications from its public version. Horaro is very limited in how much data it can manage - whilst you can use it to import into NodeCG, you will find you'll have to add a lot of data manually to your run editor, so it is recommended to use Oengus instead.
Add the schedule URL of your Horaro marathon into the box and then click LOAD SCHEDULE DATA. You can pre-populate the URL by entering it into the relevant fields of the nodecg-speedcontrol.json config file.
Next you will see a list of dropdowns. These are used to select which columns in your schedule relate to which information in the run data. The import tries to automatically select the appropriate columns, but if something is wrong you can change it here. Also available here is an option on how the players in the Players column should be split; see the Schedule Formatting documentation for more information on what these options mean and how the Players column data should be formatted. Once you have everything selected correctly, click IMPORT. An alert dialog will appear to confirm that you want to continue, and after a short loading period the runs will load into the speedcontrol run editor.
It is worth noting that this import will overwrite all existing data in the run editor - if you import your Horaro schedule, add extra details to the runs, then import the schedule again, the extra details will be lost.