I need help/guidance in formulating a speech about how social media changed the world.

The first thing to decide about this speech is the genre. I would guess that the speech is either going to be an informative speech that gives your audience a basic overview of how social media changed and impacted the world, or the speech is going to be a persuasive one that attempts to convince your audience that social media changed the world in good/bad ways. This needs to be the first decision, because the speech genre will affect certain delivery choices.
Since I don't know the genre, I am averse to giving specific information about social media changing the world. The information I provide could be way off the point that you are trying to make; however, I can definitely help in building the format of the speech.
No matter what the genre of the speech is or what it is attempting to do, the first thing out of your mouth matters... a lot. This is called your attention-getter, and it's a critical component of all speeches. If your audience is bored from the first spoken sentence, you have lost that audience. Fortunately, there are 5 types of attention getters that are typically quite effective.
Ask your audience a question. This almost always begs audiences to at least raise a hand. This response gets them physically and mentally engaged. They can't help but try to answer the question in their heads.
Use a definition. This is the weakest of the 5 in my opinion, but it can be effective, because audience members are immediately curious as to why that particular definition is important.
Use a quote. This is similar to a definition, but I find it more effective. The reason is that audiences automatically figure the quote is important if a speaker is choosing to use the words of somebody else. It's especially effective if you announce to the audience that the quote is from somebody that they consider famous or important.
Use an anecdote. People love to listen to stories. A story/anecdote allows you to paint your audience a picture or a scenario that they might be familiar with. This kind of thing really engages the mental faculties of an audience.
Make a bold, controversial statement. Fair warning, this could backfire. The goal is to emotionally engage your audience, but it could be dangerous if the audience immediately believes that you are so wrong that you shouldn't be listened to.
Once the attention getter is complete, your goal is to present your information while keeping your audience engaged. Keep in mind that what you say isn't likely to hold audience attention for very long. How you say it is more important. Use the following tactics to keep your audience engaged.
Platform movement. Don't stand behind the podium the entire time. Work the room by moving from one side to the other. Your movement forces audiences to visually track you, and this keeps them engaged.
Make eye contact with all parts of the room. Any part of the room that feels they are being ignored will begin to not pay attention.
Modulate voice volume, pitch, tone, and pace. Monotone speakers put audiences to sleep.
Use gestures. This could be easily done with your speech topic. Chances are that you will be listing off ways social media has changed the world. Number those off with your fingers as you go.
Signal your conclusion. In writing, the reader can see that he/she is on the last page or paragraph. In a speech, the audience has no clue that you might be close to the end. You have to signal it by saying something like "in conclusion." This alerts your listener to really pay attention.
Write out transitions from topic to topic word for word. Practice those repeatedly. It looks very unpolished if a transition is jerky. Smooth transitions better sell your speech and your credibility to your audience.
Practice, practice, practice. Good speakers give good speeches because a speech is a performance.
https://www.extension.harvard.edu/professional-development/blog/10-tips-improving-your-public-speaking-skills