Google "Jailbreak iPhone 4S [what IOS version you have, way to check is go to settings, click on general and click on Software update, even if it's up to date it'll tell you what iOS version you have]".I suggest you use winter board, you'll get Cydia and winter board, in the winter board settings you can turn on the summer board add-on, made for older themes. Another thing is are you SURE you want to Jailbreak your iPhone? The warranty on the iPhone will go void and you won't be able to get it replaced OR fixed if you drop it, or get it wet or crack the screen. .Here's another tip: If you ever, EVER, want to remove the jailbreak, connect it to a laptop or computer that your iTunes is authorized with that computer with, go ahead and run a software update ONLY if you want to remove the jailbreak then it'll suggest you erase all the memory on it. An extra thing is to use iCloud with most of your apps, music, contacts, and pictures so if you HAVE or WANT to remove the jailbreak and you end up erasing all memory when you do then you lose little to nothing when that happens.
Is your device running the latest version? 6.1.3 you can check by navigating from: Settings > General > about > Version ( scroll ) . If you are running 6.1.3+ then... There is not currently a jailbreak for your firmware.. There's a tether but when it turns off, you'll have to use a program to bring it back to life again... Wait till the untether ( original ) which comes out soon.. But please do not attempt jailbreaking if you are running 6.1.3+ other softwares have claimed to have jailbroken the new versions.. Please do not do so.. For there may include viruses, steal info, or simply not work... If you have more questions, you can comment or send my an message via email located in my profile info... - Cydia Dev, iSchools - Hope this helped!!