I’m not sure how you have your desk top set up. I have it showing the pull down menus rather than the big icons, but here is how to do it.
Use the “format” menu to find “text size”. Open that to select or make the text size that you want to be current in the drawing.
Then access the “dimension style” also under the format menu. Either select one that you are familiar with or set up a new one. You will have to choose the font, arrow size, and the scale (scale is in the “fit” tab when you modify the dimension style).
I keep a drawing that has all of the fonts, linetypes, and dimension styles that I use so that I can insert it as a block into any drawing. Although all of those are in the drawing block, I erased them so that they don’t show up when inserted. In other words, when I import that block containg the font, linetypes, and dimension styles, it puts the option to use them into the drawing without littering your drawing with text, lines, and dimensions that you’ll have to erase after insertion.