How to jailbreak I phone?

I have an iPhone 7plus. I'm know like nothing about this so please tell me step by step in detail instructions. I will give you best answer! Also something that won't mess my phone up

I'm not going to write a step-by-step guide for you. And plus, if you know nothing about it, why would you even do it? You can damage your phone if you don't know what you're doing.

Apple makes it very difficult to jailbreak, so you'll need to know what iOS version you currently have.

I haven't been keeping up with jailbreaking lately, so I'm not sure if there's a current jailbreak for iOS 10.x.x

Look up Redmondpie and the YT channels iDeviceHelp and EverythingApplePro; they have pretty good videos regarding iOS jailbreaking and how to do it.

If you're worried about "messing up" your phone, then jailbreaking is NOT for you. While it is pretty difficult to permanently damage the phone (but not impossible) with a jailbreak, it can bring a whole host of other problems from security issues to stability issues if you download incompatible tweaks/apps.

If you do it yourself, there's no method that can guarantee that your phone won't be messed up afterward. Jailbreaking is certainly possible (for many phones), but the most successful jailbreaks are done by people who know that they're doing. Likewise, many of the unsuccessful attempts (the one's that leave the phone 'bricked') are done by people who really don't understand the technology.

Step-by-step introductions are available online. It's not possible for us to give step-by-step instructions here, because the process varies by exact phone model and the currently installed version of iOS.

Haven't jailbroken in about 1/2 a decade but you could try checking http://iclarifed.com/jailbreak to see if & how to do so.