1) Create content-First of all create a unique content, wikipedia never accept copied contents. An article need to contain at least 600 words, because never accept tiny contents. Go for the subjects in science, history, social etc rather than make money, get paid etc because wikipedia is an encyclopedia in which it is looking forward to promote general knowledge contents so your topic is need to be a knowledge related content.
2) Create a wikipedia account-Create a wikipedia account by sign up on the wikipedia it is very easy to get a membership on wikipedia. After you are registered with wikipedia you have the right to post contents, edit contents, adding more information on other contents etc with the review of the wikipedia.
3) Post the content-After sign up you are allowed to post contents in the wikipedia. When you post the content you should have to be careful to provide a suitable title, description, images etc. You are allowed to place the reference source of your content. If you referred the content from any other sites or you have done it with the help of your own work which is done earlier in your blog then provide the url of the page. If you referred using any books then provide the name of the book.
After pasting the content in the content box and filling all the column in the correct way then sumbit it to wikipedia.
4) Wait for the approval-After posting a content on wikipedia it would not be automatically published unless it is reviewed by the wikipedia team. So that you have to wait for the email from wikipedia which is telling the status of your content. If your content is good and wikipedia accept it you have successed in your work. If not you are allowed to edit the content and resumbit it to the wikipedia once again.
5) Share the content-After getting approval from wikipedia you have to share it with your social media. It is not a part of posting but it is a part of promoting your content. If anybody searches on the internet with a keyword which is related to your content then the first result will be your content because wikipedia has a google pagerank of 9/10.
This are the steps to post a content on wikipedia. Like this way you can create backlinks from the wikipedia. All the best.