Update SDDS XB install instructions

Updated and working for me but would be good to get a review by someone else.

Sarah found some issues so moving to needs work

Updated with new theme-install screenshot, fixed some grammatical typos, and adjusted spacing in some areas to increase legibility. Setting it to 'Needs Review'.

The changes look good, thanks!

Note that I just updated the recipe command per this recent merge:

📌 Combine SDDS recipes and add core dependencies Active