No reminders after importing .ics file

No reminders after importing .ics file

I imported events from another calendar in the form of an ics file and all events have migrated perfectly into my calendar. I have set the email address to which I want reminders to be sent. I am not getting any reminders. Is there a way to set all events to have reminders sent or do I have to go through each one and set it individually? I'd like to get a reminder of the next day's events around 4 pm the day before.