I don't know if it's available where you are, but in the UK we have an annually updated book, "The Writers' & Artists' Yearbook". This volume lists writers' agents' specialist interests or fields of operation, i.e., children's literature, adult, crime etc.
Ask your local library if they have the US/Canadian/Australian equivalent. In the UK version there are also Irish agents. Agents specify in their entries how you should contact them, by letter or e-mail, with or without printed sections of your book(s) or whether they just want a synopsis. Follow the instructions carefully because they might just file your contact, and sometimes you're left waiting. Some don't answer, but persevere.
It might be advisable to look through your MS or have someone else read it before submitting it or any part of it to an agent. As I've mentioned elsewhere, Joanne Rowling was lucky - she'd sent her MS to a publisher and they'd stored it in their basement, just by chance come across by a visiting agent as he waited to speak to someone - but by and large the agent is the preferred route.
Or you can self-publish. I use New Generation Publishing. They've got a website (whatever you do, don't go through Authorhouse). The choice is yours. .