Visit the CDC's website to learn what vaccines you should get. Check your state's laws to learn what vaccines are required for your child to attend school. Talk to your doctor about which vaccines you should get and when, and to make sure that it's safe for you to get vaccines.
If your doctor's office can't provide vaccines, pharmacies often have some of the most common ones available.
Visit the resources section of this website for a lot of helpful links, or search the internet for information. Remember that something doesn't have to be true to be on the internet, so evaluate the quality of the source and think critically about the information (and that includes the links on this site).
If you know someone who hasn't been getting vaccines, talk to them about it, if you are comfortable doing so. If they just don't see the point, explain the purpose of vaccines and why it's important for everone to get them. If they are concerned about safety, explain that vaccines are thoroughly tested, and any risk of harm from a vaccine is much lower than the risk of harm from the disease that it protects against. Explain that common concerns about vaccines, like that they cause autism, are myths and have been disproven. (Visit the resources page for more on that.)
Do not attack anyone who hasn't gotten vaccines. Calmly explain why vaccines are important. You want to teach them about vaccines, not punish them for not already being vaccinated. The goal is for more people to understand the importance of vaccines. Being confrontational is likely to cause the person you're talking to to be more reluctant to listen to you. Also remember that some people, such as those with compromised immune systems, cannot get vaccines.