The patch has to be downloaded, applied, and the code tested, that it builds.
All tests must pass.
Then you have to look at the patch itself and see if you agree with the changes. This means:
o You think that it will not break anything in the future.
o It is well documented what it does.
o There are tests for the new functionality (important!).
Then you have to use your judgment and say what you think about it, and give it +1, or -1.