I use WSFTP.com for an FTP (file transfer protocol) program. It cost me around $50, and I've had it a long time. However, before you spend money, there are some free options out there you can locate with a search on Google for FTP software.
Your blog hosting service probably also has an FTP client built in, so you may be all set once you locate it on your hosting service site. Either way, you need a way to upload multiple files at a time to your host.
This is a screen shot of my WSFTP Pro screen. The left side is what is on my hard drive, and the right side is what is up on the site server.