Answer:
Writing the essay for you would be considered cheating, but I can certainly get you started.
First, you must decide what you think freedom is.
Is freedom the right to do whatever you want with no consequences? Or is freedom only the right to express your opinions so long as you don't hurt others?
Thesis: Freedom is [insert your personal views]. Other people might disagree because they think [insert a disagreeing view] but this is wrong because [support your side].
Here is an example thesis:
Freedom is the right to express your opinions so long as you don't hurt others while doing it. Other people might disagree because they think freedom is the right to do whatever you want with no consequences, but in reality, that would give people the right to hurt others, which undermines people's right to be safe.
(please keep in mind that if you use anything I provide as an example here it would be best to reword it, or else your teacher might write you up for plagiarism. I also encourage you to make your own views.)
To plan the parts of your essay, the main thing you need is reasons that you are right. The entire essay revolves around supporting your own views and debunk others.
Your supporting reasons should have already been stated in your thesis. Go back and find them. Start the next paragraphs with those reasons. Because 300 words is a very short essay, you probably only need two reasons and a conclusion.
Topic Outline:
Paragraph 2 - your argument (support your thesis)
Paragraph 3 - counterargument (why the other side is wrong)
Continuing my example above, here is an example topic outline:
Paragraph 2 - being able to safely express your opinions is the meaning of freedom. This is because being unable to express yourself means you would be restrained, which is the opposite of freedom.
Paragraph 3 - although some people think that true freedom means not being help responsible for your actions, this is not true because that would hinder the freedom of other people (include an example, like, the freedom to commit arson would harm the business or residents of the place you burn down, which means you have taken away their freedom to be safe)
Again, please express your own personal opinions and write in your own personal style.
I hope this helps you. Once you've done step 1 (the prep-work) writing the essay will be easy.