Welcome to this highly addictive hobby!! You've come to a place with a lot of highly talented and skilled modelers that will gladly provide you with tips and pointers on how to complete your projects. Have you decided on which genre or type of kits you are planning on building?
As for obtaining supplies, there are many online retailers for plastic model kits to choose from, just do a search for them and take your pic. I have a few that I prefer over others, but I am not going to post those publicly, and everyone seems to have their preference. If you would like to know which ones I've had the best luck with, shoot me a private message and I'll gladly give you the sites that I visit.
There are also some brick and mortar stores in the US that seem to have locations across the country that sell modeling supplies. If you have a Hobby Lobby or Michael's nearby, you can pick up good starter tools and kits and they often have discount coupons available.