There are two levels of training offered for those new to learning EFT (i.e. haven't taken a Level 1-2 training before).
The first is the Level 1-2 training. This class teaches you all of the foundational EFT techniques, and also gives you time in class to practice. That said, most find it an intensive course and don't feel they gain mastery in the more advanced/nuanced skills after the training. This is normal - it takes many, many practice sessions to really get a handle on using EFT with others.
After a Level 1-2 training, you can use tapping on yourself, and with friends or family. (I advise caution on using it ongoingly with friends and family as this will profoundly change your relationship to those people and is often not appropriate for ethical reasons.) If you are a licensed mental health provider , a certified coach, or other wellness professional, you can begin incorporating it into your practice. But if you're not trained to work with trauma, it wouldn't be appropriate to do so with EFT after just a Level 1-2 training. Working with trauma required additional training, practice and personalized feedback which is provided during certification.
If you plan to use EFT as your main modality, or want to be able to call yourself an EFT Practitioner, then you should get certified for your safety and that of your clients.
During Certification, you'll complete 50 practice sessions, 4 case studies, receive ongoing personalized mentoring, and be able to attend further training in an online group class. All of these elements will support you to work the kinks out of your EFT practice, learn how to handle challenging cases, respond appropriately to clients with trauma, and be able to deliver the right techniques at the right time during your sessions. Like riding a bike, this is not something you can learn by watching or reading about - it takes practice, including falling off the bike!
Following successful completion of the Certification Program, you'll be eligible for accreditation by EFT International, and be able to list yourself on their directory as a Certified EFT Practitioner. You'll be able to safely use EFT with your clients and groups of people on a nearly endless variety of issues (within your scope of practice).