How to downgrade my iphone 4 CDMA ios 6.1.3?

Help me please!

How can I downgrade from IOS 6.1.3?

Added (1). How can I download shsh!

or is there any way?

Added (2). How can I download shsh!

or is there any way?

If you didn't save shsh blob file its impossible if you did then shift+restore and locate the file and restore using it

Well downgrading is not supported by apple at all but in some previous versions you could downgrade using special softwares. Now for ios 6.1.3 I think there are some ways to downgrade
http://www.letsunlockiphone.com/downgrading-latest-ios-6-1-3-saved-shsh-blobs/
but I can't assure you that it will work.

To downgrade u first get the version you want then you hold alt or shift when clicking restore on your pc try both it changed from wether your on mac or pc then select the old vrsion you want and then you can downgrade to that version. To get ssh you need to first jailbreak your iphone 4 then after that you need to download cyberduck onto your pc/mac and then you get openssh from cydia now you can ssh. Can change whatever you want if you know how to.