Apply Articulations to multiple notes

Select the bar;
Double click on the articulations.
Or: hold down CTRL;
Click the notes;
Double click on the articulations.

select all the notes you want to attach the articulation to and double click the item in the palette or use the shortcut if one exists. You may need to see https://musescore.org/en/handbook/selection-modes for more info.

Select these notes (see: https://musescore.org/en/handbook/selection-modes) and add these articulations.