Need some basic answers please, and thank you!

1. Add text frame (to input the title) to the beginning of each song. You can find it in the Frames palette. Drag and drop to the first measure of each song. Or select the measure and click the element in the palette.
2. Select the measure(s) you want to delete and press Ctrl+Delete.
3. Select the measure which you want to be the last of that line, press Enter or attach the line break element from the Breaks palette.
4. It cannot be "deleted", but it can be hidden. Select the rests and press V, or untick "Visible" in the Elements Inspector.
5. Do you mean adding a time signature of 3/4? If so, attach it to a measure from the Time Signatures palette.

In addition to the above:
1. End each song with a section end break from the palette as well. It'll prevent courtesy accidentals/clefs/time signatures from showing up. It'll also ensure that repeat/jump references are handled within each section first.

5. You don't. A whole rest takes up 4 beats, which doesn't fit within a 3/4 measure. However, what you're looking for is probably the "full measure rest", which takes up the duration of the full measure, regardless the time signature. It is displayed using the whole rest symbol, but is center aligned within a measure rather than left aligned.
   MuseScore fills your measures by default with such rests, but see https://musescore.org/en/handbook/measure-rests if you have to manually recreate them.

Re: #3

This may be of help for hand writing music:
Blank_Staff_Paper.mscz