Resolve "Edit CLI documentation"

Closes #24 (closed)

Changes made:

• Added introductory sentences and a section on opening CLI
• Made some edits to the headings and layout to improve the documentation flow/readability for readers
• Edited the instructions and added some extra explanations to clarify some parts

Things to note:

• Some of introductory info and explanations that I added (mainly about scp and rsync) should be fact checked -- I tried to find the most accurate info that I could by checking some online sources