Lots of red pen.
That’s what editing looks like. Below is the first few paragraphs of Saturn: Journey to the Core, which one can use as an example for what editing physically looks like. Many of the firsts words I deleted entirely. The first sentence below isn’t in the completed story. I changed the beginning entirely when I was editing. “What do you think of going to Jupiter?” are the first words now in the story, which I wrote in red during the editing process because I didn’t like the original first line.
Don’t be afraid to cut entire sentences during the editing process.
If there’s a sentence or a word which isn’t working for the story – or even an entire concept – then it isn’t working.