Supreme Court Justices are nominated by the president and confirmed by the Senate. Once they are approved, they have lifetime terms.
I agree, and believe anyone would agree, with the quote. Getting a Supreme Court Justice nominated and approved, who shares your political views, means that you will have a very powerful person in the Judicial Branch exercising power for potentially several decades. Supreme Court Justices, especially through the power of judicial review, can exercise great power over the government without having to worry about reelection and with no end to their term. This means that the president, by extension, enjoys great influence over government through his nomination of these justices.