Adding Voice Notes

Welcome to MuseScore.

MuseScore works best when you enter notes left to right - as you read them.

So, first enter all the notes in voice 1.

Then go back to the start and press the voice 2 button - see your picture voice notes.jpg which shows the voice 1 button pressed and shaded blue. Voice 2 button is to the right of that and should be shaded green when pressed. You may not be seeing the voice 3 and 4 buttons. They are very rarely needed and are only shown when you activate the "Advanced" workspace.

Having successfully found and pressed that button start entering the notes in voice 2.

And that is it.

But... I can see from your picture TEST.JPG that you have some measures that have durations shorter than the indicated time signature. They have small grey "-" signs above their right hand end. Possibly you deleted a note with CTRL+DELETE rather than just DELETE. with CTRL deleting something removes the time associated with it and shortens the measure. You usually want to keep the length of measures in agreement with the time signature so don't use CTRL with DELETE unless you are trying to do something out of the ordinary.

Another tip. Read the handbook through at least once to get a clearer idea of how MuseScore does things and to know that it contains all the tips you are likely to need, albeit that some are difficult to locate. It is pleasing to see that you have already found the advice on how voices work.

Another tip. It makes it easier to offer help if you attach a score (.mscz file) rather than pictures. Then we can see more clearly what you have done. So, if after reading these replies and the handbook you are still stuck, come back with a copy of the score and explain what you are having difficulty with.