There are three levels of licensing for Amateur Radio: Technician, General, and Extra. Each offers progressively more privilege with Extra being the highest.
Studying for a licensing exam is straightforward and is often self-directed. ARRL training guides are available as both spiral bound books (T, G, E) or for Kindle download (T, G). ARRL also offers Q&A study guides for all three license levels (T, G, E). These manuals teach material you need to understand licensing at each level and list questions from the test pool for exam prep.
The current question pools are available here: https://www.arrl.org/question-pools
There are a variety of online study resources. Be sure the one you select covers the current year!
HamStudy.org - Sign up for a free account to access Study Mode and practice tests. This site also offers a variety of information about the hobby and other resources.
HamExam.org - Offers a complete list of current exam questions, flash cards, and practice tests.
HamTestOnline.com - Allows free 'try it' practice tests, with full study available for purchase.
Classes are also availble - usually online. ARRL lists options here: https://www.arrl.org/find-an-amateur-radio-license-class. We suggest entering your ZIP code and select "250 miles" from the drop list to get everything including online classes.
We'll be honest - it's possible to take and pass the exams by memorizing questions. However, just memorizing, you'll miss important parts of the 'why' that teach you about FCC regulations, good operating procedure, and radio electronics. Yes, practice tests are important for building confidence so you pass the first time but consider learning the background material, too.
FCC licensing examinations for amateur radio are adminstered by local Volunteer Examiners.
ARRL lists currently available testing sites and dates here: http://www.arrl.org/find-an-amateur-radio-license-exam-session
There are several steps to get ready for testing:
Study - learn the material for the license you'll pursue
Select a test site and contact the exam coordinator so they can provide you any special instructions or tips.
Get an FCC Registration Number (FRN) - You must apply for and receive an FRN before attending a testing session. Here's how.
File for a license - TALK TO YOUR EXAM COORDINATOR and learn whether they will file your license application or if you will do it.
All amateur radio licenses (Form 605) are now filed online through FCC's Universal Licensing System (ULS). Register for a CORES account and secure your FRN first, then create a ULS account to apply for your license. There is a filing fee - the current list is here: https://www.fcc.gov/personal-service-and-amateur-application-fees
On test day - Bring an acceptable photo ID like a driver's license or passport, printed copies of FRN and ULS paperwork, and a good pencil with eraser. Arrive at the test site a few minutes early to check in.
NOTE: many in-person test sites will allow you to take one, two, or all three tests at one sitting for a single testing fee. It's worth considering!