In the original import file sent to you at the implementation stages, this spreadsheet will already include the first, middle and last name fields for you already.
If your data quality is good, and are confident you know the first, middle, last name format, then please utilise this process for individuals. This is due to increased screening accuracy from the system algorithm from separating the names. You should continue to use this technique unless you are really unhappy with the data quality.
When the data quality is extremely poor then utilise the last name field for the full name string. But as a rule of thumb, please enter the name as it would be shown on the individuals personal identity documents, using the last name for the full name is a last resort.
And for when screening an entity, please only use the last name field.