Sorry to be the bearer of bad news but the major agencies do not accept unsolicited submissions.
To clarify, William Morris/Endeavor, ICM, UTA, and CAA do not take submissions. The only ways you can get a meeting with them is by having numerous film, tv or theatre credits and/or an industry/celebrity endorsement. Some of the smaller agencies might have different policies. Not sure if they still publish The Dramatists Sourcebook, but if so, pick up a copy. It will help you figure out who will and will not take your submissions.