The first thing is to make sure your machine is set to DCEP Direct Current Electrode Positive.
Its easy to accidentally plug in the stinger to the wrong port so make and 7018 rods are meant to run on reverse polarity DCEP.
Next make sure your amperage is good for the size 7018 you are using.
Remember that for vertical uphill welding, less amperage is required than for welding flat or horizontal.
Thickness of metal also factors in but as a rule of thumb for 1/4" and thicker around 75-85 amps will work for 3/32" 7018 and around 105-120 will work for 1/8".
All machines are different so you might need to experiment with amperage to dial it in.
Arc force aka arc control aka dig function. Some machines are equipped with a setting that senses the drop in voltage when the arc length gets tight.
The machine automatically increases amperage a bit when the arc gets tight.
This is a good feature but not really needed for 7018 vertical. If fact, if you are a student, you might want to turn this feature off because you may not have it on whatever machine you are required to use later when you take a welding test.
Hot start is another feature that can help you not stick the rod but again, you may be better off not relying on hot start because not all machines have this setting.
Arc length is probably one of the main things that makes a difference when learning how to weld vertical 7018.
A long arc will make welding vertical with 7018 very difficult.
Your arc length needs to be the diameter of the electrode or slightly less but remember that a 7018 burns back up inside the flux a bit try holding a tighter arc than you think.
Dont jam it in but you should feel the flux rubbing on the metal.
Angle of travel for a 7018 vertical weld should be a slight push angle but angle can be very forgiving provided your arc length is good.
You should experiment with rod angle starting with a 90 degree angle and then a slight push angle to see what works best.
Welding specifications, procedures, and codes sometimes specify stringer beads with little or no weaving.
But a slight manipulation often helps to overcome the effects of gravity and helps a 7018 vertical bead to lay down flatter.
Travel speed should be just slow enough to fill in the toes of the weld so that there is no undercut.
Too slow a travel speed will build up and sag on a vertical uphill weld.
Too fast a travel speed will leave undercut.
There are many more videos and articles here at welding tips and tricks on how to weld vertical 7018.