What does it mean to "know" something about an historic event?
You need to decide what your threshold for believing something about the past is.

Hope you had a wonderful Easter!
Over the last few weeks I curated evidence of the crucifixion, burial and resurrection of Jesus. What counts as evidence for historical events is wider than what is permissible in a criminal case. It is an important distinction I only recently understood.
Establish an historical standard for evidence
If your threshold for evidence is only what would be permissible in a trial — live or recorded testimony from eyewitnesses and physical evidence from the event, then no, the evidence is not available. The original documents written on scrolls would have long disintegrated, and obviously the eyewitnesses have died.
Trial evidence is a far more stringent standard. If mistakes are going to be made, the criminal justice system would rather guilty people go free than innocent people be convicted. Of course it doesn't always work that way, but that's a separate issue.
I'd argue that when we speak of evidence as Christians, we should be using the more relaxed standard of evidence historians use. No one is on trial. Therefore the goal for historians is to decide what most likely happened, based on the information available.
Here's an example.
Lately I've been learning a bit about Mormonism. Like Christianity Mormonism includes aspects of the religion you can test, such as whether it's reasonable to believe in the Book of Mormon. I don't think it is, given many of the reasons cited in this blog post. Even though Mormons argue they have historic evidence leading to their conclusions, I believe the facts points to reasonable doubt in how much of the Book of Mormon you can trust.
Learn how to analyze history for yourself
A great way to learn how to analyze the evidence, is to pick up books by former cold case homicide detective J. Warner Wallace. I recently finished Cold-Case Christianity, his first of three.
The book uses historic evidence to investigate whether we can believe what the gospels say about Jesus. I think even a teenager could easily read and understand the 279-page book, split into two sections. The first half explains how to use techniques of real detectives to examine whether to trust the Gospels. Learning how to build a case using circumstantial evidence, how to evaluate witnesses, how to trace whether the evidence is reliable even though a lot of time has passed since the incident, were all subjects of chapters.
The second half of the book then applies these techniques to the Gospels Matthew, Mark, Luke and John, asking four key questions:
Were the Gospels written early enough to be authored by eyewitneses?
Did other sources outside the Bible confirm what the Gospels said, even if they thought Jesus was nothing more than a normal guy with fans?
Is everything in the Gospels accurate?
Were there reasons to think the writers were biased, or in any way motivated to lie?
Wallace argues if you can't satisfy your doubts in all four of these areas, then it’s logical to reject whatever you are investigating as untrustworthy.
Share what you’ve learned before sharing books
Once you know why you believe it, you’ll steadily feel more confident in your abilities to share the Gospel with others.
I realize it is simpler to just hand someone a book or fling a five-minute video to someone’s email address. While providing resources can be useful if the person desires to dig further, you're the one with the relationship with that individual. If you can't explain why you believe something, what makes you think they will care what someone who they don't know says about it?
You don't have to know everything about a topic. But that doesn't mean you shouldn't know anything about it either. This is simpler than it may sound.
I'd encourage you to devote even just 30 minutes a day to training yourself with apologetics material. The more I evaluate the Gospels and arguments for and against Christianity, the deeper and stronger my belief that Jesus is precisely who he claimed to be becomes. This video walks you through some of my favorite apologetics books. I can vouch for books 1, 2 and 5 on his list as being excellent. I’m sure the other two are excellent as well, but I haven’t read them.