You'll need to concatenate the data going into the memo field and add a carriage return and line feed. I don't remember the global constant for these but you can always use Chr(13) & Chr(10). So, for example, let's say you want to take three fields and concatenate them into a memo field, you could use an append query and the following syntax for what you want placed in the memo field putting a carriage return line feed between each:
Expr1: [Field1] & Chr(13) & Chr(10) & [Field2] & Chr(13) & Chr(10) & [Field3] & Chr(13) & Chr(10)