You can easily change the WordPress url by going to settings tab in the admin panel.Follow the below steps
Step1:Login to your admin panel by following the link http://ursite.com/wp-admin or if you hosted in sub directory or sub domain just go to link http://ursite.com/directory/wp-admin
Step2:Once you are login to your dash board click on the settings tab (Refer the right side picture)
Step3:After you enter into the settings tab you will view a new window.in that window just change your WordPress address and site address as your site url
You can refer the below picture for the above process
Moving to a sub directory
To move into a sub directory you need to follow the above steps.Fill the WordPress address and site address as your sub directory.
After changing the url just click on the button save changes.Please don’t load your site at this time.
After changing the url,copy all your files from the host to the sub directory where you want to move your WordPress blog.for example http://ursite.com/blog.
Note:You have to change your uploaded contents urls manually bye editing each and every post
You are done now your blog is migrated within the host.
Migrating WordPress from one host to another
To move your WordPress from one host to another you need to copy the backup of database and the files
To copy the database go to phpMyadmin and export your database.and go to your new web host and go to the same phpMyadmin and import the database backup into your new database.
After that copy all your files and folders from old host and upload it in your new host.by finishing your upload process edit the wp-config file with your new database settings..