You'll need to do a separate import for each table that you've split your original table into and make sure you import the linking key value as well or run an update operation just after to the import to add it if you can't import it.
To select a different table when importing records manually, first select a layout that refers to the desired setup in layout setup... Filemaker creates such a layout for you each time you define a new table, so you should have these layouts already created unless you deleted them. If you deleted them, just create a new layout that refers to the table.
I tried doing the one table with the text file I'm importing and it brings each line in as a record (which I knew it would), but I don't want each line to come in as record. I want all this information to come in as part of one record. How would I do that?
Also, my list of fields from the text file goes vertically in my layout and would like to import the file in the one layout/record, is there a function/calcuation for each field to recognize the correct area?
Filemaker will expect each row to represent one record during import and that fields will be organized into separate columns. If your data is not arranged in that format, you'll need to either Edit the file into this format, Import the data into a different table and use a script to move the data into the correct fields and records of your tables or there may be a way to do an xml import with an XLST grammer that extracts the data for you.