Sure, being in master branch all you need to do is:
git merge <commit-id>
where commit-id is hash of the last commit from newbranch that you want to get in your master branch.
You can find out more about any git command by doing git help <command>. It that case it’s git help merge. And docs are saying that the last argument for merge command is <commit>..., so you can pass reference to any commit or even multiple commits. Though, I never did the latter myself.