I can perfectly align text from left to right, however, I can't seem to find how to align text from top to bottom in a text box. Help?
Unfortunately there is no command to align text vertically in Muse.
Muse is en of life and not being developed any longer. At the risk of being flamed for saying this, my advice is to quit using Muse now and learn to code with CSS Flexbox This will give you simple but precise control over vertical & horizontal alignments without kludgey hacks & workarounds. Simple HTML and CSS is all you need.
Unfortunately, Muse doesn't know what Flexbox is. But Dreamweaver and modern browsers support it just fine.
Nice, Nancy! Muse indeed doesn't know, what flexbox is, but you didn't really answer the orininal poster's question. He doesn't want to center an element, but text within its text box. (Yes, I know this appearence(!) is achievable with flex box too, but not as simple as one would expect.)
And: The question was not, which tool to use to achieve this. The question was, how it can be done with Muse.