How to do more than one mesure of rest please?

Have 6 empty measures in a row, then press M. See https://musescore.org/en/handbook/measure-rests#multimeasure-rest

Note though you normally don't have to do anything special to make this happen. When you create your full score, just have the six measures of rest for whatever part this is, but when you generate the parts from that score using File / Parts, multimeasure rests are created automatically. You'd only need to actually enable them manually if you are for whatever reason entering only a single part rather than a full score.