To make an event recurring with a fixed pattern, press the repeat button in the event editor.
This will add a new section in the editor, where you can set the base-interval (day, week, month, year) and details (depending on the selected base-interval) and optionally an end end date our number of repeats.
To create an event every 2 weeks, you can set the base-interval to WEEK, then set the frequency to every 2 weeks (or select DAY and every 14 days).
For irregular events, e.g. flexible shifts, you can use the multi copy function, open an event, press copy and select the days for the event to occur.
If you have problems with recurring events, please see Recurring events do not save.