from
"From the very first": (Greek, "anōthen", "from above)." So translated in (John 3:31); (John 19:11); (James 1:17); (John 3:15); (John 3:17). In no other place is the Greek, "anōthen", translated "from the very first." The use by Luke of anothen is an affirmation that his knowledge of these things, derived from those who had been eye-witnesses from the beginning (Luke 1:2) was confirmed by revelation. In like manner, Paul had doubtless heard from the eleven the story of the institution of the Lord's Supper, but he also had it by revelation from the Lord (compare (1 Corinthians 11:23) and his writing, like Luke's "anōthen" knowledge, thus became first-hand, not traditional, merely.
understanding
(Greek, "parakoloutheō", literally, "followed alongside of"; or "closely traced".)
in order
The words "in order" are emphatic, indicating Luke's purpose to reduce to order the Gospel story.