Here’s the part why it takes most guys several tries to get this to work, other than missing the hole.
A good weld requires clean, shiny metal, so all of that wd40 or deep creep or other penetration lubes we spray on it don’t help. If you’ve done that, spray it with some brake parts cleaner and let that dry.
Then, take a steel pick or screwdriver and scratch the head of the broken screw until most of it shows shiny metal and not the dark carbon deposits that build up around it.
Cheap welders usually have settings for metal thickness. Most don’t go above 1/4”, but that’s not relevant for this. Chances are, you’ll plug it in to a 120v outlet, set it to max, and blow your breaker in 1.5sec. Instead, if you have a generator, plug it into that. If you don’t, try setting the welder for half of it voltage dial and half of its wire speed. That should be enough to let it burn for at least 3-4 seconds a couple times per minute as you burn then inspect, then repeat.