This is a good question. The most important part of any essay is a thesis statement. In this case, you will have to create a thesis statement that is based on the text or texts that you are assigned. For instance, if you are writing on Homer's Iliad, your thesis might be that the gods and fate overrule the wills of the main characters.
Of course, this thesis can be debated. This is a good thing, because all thesis statements should be debatable.
What you need to do next is to add supporting statements. In other words, what is your proof for your thesis statement. This is the bulk of the essay. The better your arguments are, the better and more convincing your paper will be.
Finally, you will need a conclusion. In this conclusion, do not seek to add something new or an innovative twist. What you want to do instead is summarize your findings. You may want to restate your thesis in view of all the evidence.
First, a "text essay" is a written response to text that you have read. It may be on a test or a homework assignment where your instructor asks you to select a question to write on or provide reactions to a reading assignment in essay form.
Writing any essay is a series of steps:
Determine the topic -- if you have several questions to chose from, review each and select the one you can write on with authority.
Brainstorm -- I like using a schematic math with my main topic or theme written in a bubble in the center of a piece of paper. From there I jot down thoughts about the theme. There are no bad ideas at this point. Jot down everything that comes to mind.
Organize your thoughts -- Your thoughts are on paper, and you can use those to organize your ideas and develop an outline.
I) Your first main idea
A) Your supporting information
B) More supporting information
1) details that add to the reader's understanding
2) additional details
II) And so on . . .
See a good English textbook for detailed information on formatting an outline as the above ignores most of the rules of outlining!
Write -- your outline becomes the map you'll follow to write your essay. You'll need an introduction to set the stage for your thesis statement which will explain what you are about to write. Every component of your essay needs to be related to your thesis statement and in the same order that you indicated in your introduction. If you think of information you didn't include in your outline . . .
You'll revise -- revising is reviewing your paper for logic, clarity, grammar, and editing your thoughts.
This all gets dicey if you're trying to respond to an essay question on a test and time is an important factor. So, before the test date, review your notes and try to figure out what your instructor might ask and write a few sample essays for practice.
If you are writing a paper with a future deadline, you'll be able to more adequately brainstorm and create an outline to work from. You'll also be able to get assistance from your instructor if you have questions, visit your school's Writing Lab, and/or have a peer review your paper and edit based upon the recommendations you decide to accept.