Process for creating a SharePoint Master Page from a HTML page.

1. Create your HTML master page on local with proper styles. 
   Check if this HTML page works on all browsers. Especially on IE and Chrome. For Office 365 sites also check for Mozila.
   
2. Go to Site Action --> Site Settings --> Web Designer Galleries --> Master pages and page layouts. 

3. Create a folder for your master page and upload all your master page files. 

4. While uploading the html page select the "HTML master page" from the drop down. And for other files select "Custom".

5. After successfully uploaded all the files. Go to Site Action --> Design Manager --> Edit Master Page

6. Find your master page folder here which you have created in "Master pages and page layouts".

7. Open the folder and select the HTML page and on the top click "Convert an HTML file to a SharePoint master page".

8. It will open a wizard, there again go inside your folder, select HTML file, click insert. 

9. After insert you must see the conversion successful message status for that respective HTML page. If you are getting conversion error, don't try to publish as major version. 
   Correct the HTML file, upload again. Only publish when you get conversion successful message. 

10. Now your master page is created. But it is not yet listed in the master page list(Site Action --> Site Settings --> Look and Feel --> Master Page). 

11. To make it listed on the master page list, right click on master page and select "Publish as major version".

12. Now your master page is listed. To change the master page, go to Site Action --> Site Settings --> Look and Feel --> Master Page and select your master page from the dropdown.