There are several ways.
If the data is separated by a delimter (e.g. a comma after first name, last
name, street, etc.) you can easily use Data>Text to Columns. You can still
use it if the data isn't that clean but you may have to start with fixed
length to get as close as you can, then cleaning it up manually.
The other option is to move it to Word and do a series of Find and Replace
actions to get a delimiter in there (after convering the table to text), then
convert back to a table and copy back into Excel. Annoying and a last
resort, but I've had to do it many times.
Hope these get you started!
--Elizabeth