As an adjective:
* "Water is essential for life." (It's absolutely necessary for survival.)
* "The essential ingredient in this cake is love." (It's the most important ingredient.)
* "It's essential that you get enough sleep." (It's absolutely necessary for your health.)
* "This book is essential reading for anyone interested in history." (It's highly recommended for anyone interested in the topic.)
As a noun:
* "The essentials for a camping trip are a tent, sleeping bag, and food." (The most important things needed)
* "He packed only the bare essentials for his weekend getaway." (The most basic necessities)
In a phrase:
* "This is essential to our success." (It's absolutely necessary for us to achieve our goal.)
* "It's essential that you understand this." (It's extremely important that you comprehend this information.)
You can also use the word "essential" in a more figurative sense:
* "He made some essential changes to the plan." (He made important and necessary changes.)
* "The essential part of the story is the hero's journey." (The most important part of the narrative.)
The specific way you use "essential" will depend on the context and what you want to emphasize.