Reestablishing Automatic and Secure FTP Connection, Primary Domain Change

It is usually either safe and secure or user friendly, very hard to have them both. In this case what you ask means that PHP can write to wordpress folders which means that any bug in a plugin or theme might be escalated to a full control of your site.

If you still prefer to be less safe and secure, you should check the permission of the wordpress directories to make sure the web server is allowed to write to them. The codex is a good place to look for inspiration – https://codex.wordpress.org/Changing_File_Permissions