How do I move the sidebar more to the right in TwentySeventeen?

You have 2 options:

Option 1.

Just add negative margin to the sidebar CSS like this:

@media screen and (min-width: 48em){
    #secondary{
       margin-right:-150px;
    }
}

Option 2.

Add more max-width to the wrapper:

@media screen and (min-width: 48em){
    .wrap{
        max-width: 1340px;//the default is 1000
        padding-left: 348px;//you have to add padding left so the left side doesnt move, the amount needs to be proportional to the amount of max-width you are incrementing
    }
}

i added the media query, its needed so this CSS doesnt affect the mobile view.