Can't speak specifically for Goldman or MS, but most companies differentiate between campus hiring and "experienced" (aka non-student) hiring. Campus hiring targets current students and generally happens on an annual cycle to fill expected entry-level positions. All the open positions are filled through this cycle so applying off-cycle is a no-go. For experienced hiring - which you probably fit into since you've been out of school for a few years - you can apply at any time, but there needs to be a specific job opening for you. Usually you can either apply specifically for a posted job, or just submit your resume and if HR thinks your skills are a match for a current or future job posting they'll contact you.
Your best approach is to try and find some contacts at Goldman or MS (other alumni from your school, friends of friends, etc.), set up some informational interviews and start networking, networking, networking.
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