2. Go to SharePoint >> Site Settings >> Designer Manager;
3. Go to “Step 3 Upload design files” and Map the following location as a network drive so you can work easily with your design files: http://yoursharepointdomain.com/_catalogs/masterpage/
4. Go to “Step 4 Edit Master Pages” and “Convert an HTML file to a SharePoint master page”;
5. After it’s converted to master page, go to the mapped drive and then open the .html and .css file you uploaded; Modify them as needed.
6. Once you are happy with the result, Go to “Step 7 Publish and Apply Design”
1) “Go to the Master Page Gallery” and publish the .html file;
2) “Assign master pages to your site based on device channel”
Once it is published, you can still modify the .html and .css file.
if you want to hide the header and footer in popup/dialog pages, add class names “s4-notdlg noindex” to the header and footer.
If you want to display drop down menu in the top global navigation,
1) Go to “Site Settings >> Navigation”, Create a header and move sites/links under that header;
2) Go to the Snippet gallery, change the MaximumDynamicDisplayLevels (under Behavior) to 1. Copy and Paste the code into your masterpage.html file.