When writing an essay, where are you suppose to write the thesis statement?

before your outline?

in your outline (after introduction heading)

after outline?

in the beginning of the intro

or the end of the intro?

There are two broad approaches regarding the thesis statement. First is the top down approach in which the essay starts with the thesis statement (in the introduction) and carries on from there. The advantage of this approach is that it is straight forward. The disadvantages of this approach are its pedestrianism and lack of novelty and professionalism.
The second approach is the tunnel approach in which the essay starts broadly with the introduction laying out the groundwork. This approach involves introducing the topic in a general sense and gradually moving towards the thesis statement. The thesis statement is usually one of the last two to three sentences, preferably the last, of the introduction paragraph.
The advantage of this approach is that it is extremely attractive and professional. It doesn't divulge the goods in the first sentence. It builds a narrative that leads to a catchy thesis statement.
While the tunnel approach is effective, it does have a disadvantage of not suiting people who possess mediocre grammatical skills. This approach requires a grip on the thought process and structure of the paragraph, making it a little difficult to handle.

Another common practice is writing the thesis statement within the outline of the essay, usually at the very start. This approach is, in my humble opinion, mediocre and a way of getting rid of an important part of the essay in a hasty manner. However, it is hassle-free and easy to use.

Hope this helps!!!

Thank you so so much!

If possible can you also tell me, that in the outline for each subheading that we mention within the heading, do we need to write a new paragraph?

for example if my outlike

1
a
b
c
d

2
a
b
c
d

do i need to write a paragraph for a, b, c and d or can I mention a and b in one paragraph?

It is better to separate paragraphs. The more the subheads, the shorter the paragraphs will get which allows the writer and the examiner more breathing space. If, for example, you amalgamated points a and b into a single subhead, then your paragraph will be a single longer paragraph.