Here’s how it’s done:
1. Go into the WordPress dashboard and click on “Options”. Where it says “Wordpress address (URI)” enter the NEW address of the blog. Below that, it says “Blog address (URI)”. If your old address is entered in, put the new one in there too.
2. Using FTP access, go to your web directory. Change the name of the folder where your WordPress files live to the NEW name. In my case, I renamed it “blog”, where before it was “wordpress”.
3. Create another directory, and give it the old name. In my case, it’s called “wordpress”. This will be an empty directory.
4. Create an .htaccess file. This needs to go in the ROOT (main) directory of your web folders. You may already have one there. If you have one simply add this line:
Redirect 301 /oldfoldername https://www.yourwebsite.com/newfoldername
Replace the folder and site names with your own, of course. If you don’t have an .htaccess file, it’s pretty easy to make one. Open Windows Notepad, enter the line I mentioned, and save the file as .htaccess. Then, upload it to the root of your web folder.
That’s it. If you do everything right, you should be able to access your site from the new directory you wanted, all of the links on your blog should point to the new one (unless you entered them by hand), and if someone enters your old address it will redirect to your new one. Additionally, all of the inbound links counted by Google, Yahoo and the others, will transfer over to your new URL. The 301 redirect tells the search engines that the site has been permanently moved.