Even if you don't publish a paper on arxiv in the near future, it is recommended to register an account, because with it, you can see the e-mail address of the author of the paper published on arxiv website, which is conducive to communication with the author. Then, you need a post approval. The person who can give you approval must publish a paper in your field on arxiv. The easiest way is to find a paper at random, just like the abstract page. Look at the page linked by the sentence "Who is the author?" You will find it easily. You'd better find a reference from someone you know well. It doesn't matter if you don't know him, as long as you can get him to recognize your professional background and pass you. Then once you want to send your first paper, arxiv will automatically send an email to your mailbox after filling out the form, including a link to confirm the form. You just need to forward this email to the confirmer and ask him to confirm it for you. Once you receive the confirmation letter, you can publish your paper under the arxiv category. According to arxiv's instructions, if you want to modify the paper after it is distributed, you must not post it any more and replace it. In addition, after the paper is published, you can also add a classification to the paper, but don't post the paper under other classifications. According to arxiv's instructions, if your paper is written in TeX, you'd better submit the source file. However, I have seen papers with only PDF files, and Microsoft Word files are not supported.