Supposing you have a name roster as the first screen shot shows in single column below, and you need to split the full name to the first name column and last name column as the second screen shot shows.
Step 1. Select the column that you will split, in this case it is A1:A13.
Step 2. Click the Text to Column button under Data Tab.
Step 3. In the Convert Text to Columns Wizard – Step 1 of 3 dialog box, check the Delimited option, and click Next button.
Step 4. In the Step 2 of 3, only check the Space option in the Delimiters section, and click Next button.
Step 5. In the step 3 of 3, check the Text option in the Column data format section, and specify the Destination cell.
Step 6. Click the Finish button.
Then you will see the full name column in separated into first name column and last name column at once.