How to delete the current backup on my iPhone 5 and get my previous one?

I jailbroke my iPhone and plugged it into my computer to charge it and it ended up backing up with the jailbreak on it… When i went to the preferences it didn't have the backup i did before the one today (which was sometime back in december of 2013)… The most recent one it shows was from April 2013… How do I get the one i did in december?

Try using iCloud: Step are below:

Step1: Use iCloud
Tap Settings > iCloud > Storage & Backup
Turn on iCloud Backup if it's off
Tap Back Up Now

Follow the initial steps in the iOS Setup Assistant (select your language, and so on).
Select Restore from iCloud Backup when the assistant asks you to set up your iPhone (or other iOS device)
Select the backup you created earlier.

Step 2: If you've already set up your device, you can erase all current content to go through the iOS Setup Assistant again. Tap Settings > General > Reset > Erase All Content and Settings. Do this only if you already have a backup, because this step will remove all current content from your device.