、。
Don't just space out — hurry up and write it down!
Literal
Space-out-don't-[without-ないで], briskly note-write [command-なさい] [emph-よっ].
ボケッと is a mimetic for 'spaced-out / zoning out,' and (as always with mimetics) the と before する/しない is the adverbial marker. さっさと 'briskly / quickly' is another mimetic-style -と adverb with a sharpening, urging tone. ~なさい is a softened command form, less harsh than bare imperative but more demanding than ~てください; typical of parents or authority figures addressing subordinates. メモ書き is a compound of the loan メモ + the masu-stem 書き, used as a noun 'note-writing' and then as a verb via なさい.