Check out, review, and merge locally

Step 1. Fetch and check out the branch for this merge request

git fetch origin
git checkout -b username/models origin/username/models

Step 2. Review the changes locally

Step 3. Merge the branch and fix any conflicts that come up

git checkout master
git merge --no-ff username/models

Step 4. Push the result of the merge to GitLab

git push origin master