I'm confused. Are you asking how to center 5 frames vertically on the page, or how to center the text within them vertically? Or both?
If the former:
You can use Layout > Create Guides to create a grid:
Draw a frame and duplicate down once, then use Object > Transform Again 3 more times:
If the latter, select the frames (threaded or not) and choose Vertical Align Center:
If that button is missing from your Control Panel, you can find the command in Type > Text Frame Options:
Hi, thank you. That was helpful. I see now that I don't need the grid at all. I've made 5 equal text boxes and stacked them, grouped them, and then threaded the text through them (then deleted the text).
Now, the trouble is ... I put these boxes on a master page. ... When I apply this master page to a document page, and then try to add text to that document page, the cursor acts as if it can't see the text boxes. I can't actually put the text into any of the text boxes I created. Can you help with this? I've tried searching but get nowhere. I don't see anywhere that these text boxes are locked, or in a locked layer.
Oh, I figured it out! Command-Shift-click. Think I'm on my way!