If you have a single FULL NAME column that you wish to split into FIRST and LAST name columns...
First Name column formula (where A2 is where the original Full Name is):
=LEFT(A2,FIND("[",SUBSTITUTE(A2," ","[",LEN(A2)-LEN(SUBSTITUTE(A2," ",""))))-1)
Last Name column formula (where A2 is where the original Full Name is):
=TRIM(RIGHT(SUBSTITUTE(A2," ",REPT(" ",100)),100))
Then export as CSV (Values)
Import the CSV file.
Sources:
https://www.extendoffice.com/documents/excel/3270-excel-extract-all-but-last-word.html