Reset Ical alarm for whole downloaded calendar?

I have downloaded a calendar from the web for a schedule of games. I want Ical to alert me on the morning of these games – the games all start at 4 pm and I want alerts at 9 am the same day… as of now, it’s alerting me on time. Is there a way to set the alarms for the whole calendar instead of going entry by entry and changing the setting?
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Dhruv M