If you split manually...

Make a copy, delete everything but tables in new copy, remove all tables
from original copy then create links to tables in new copy.

...then your security on the back end will be retained.  If you use the
splitter wizard you will lose all security on the new file containing the
tables and will have to reapply it.

Users will need a copy of your front end and *access* to the workgroup file
used to secure it.  That would typically be put on the server and shared
just as the data file is.  Then each user will either need to join that
workgroup file to use your app or use a shortcut that specifies it as a
command line argument.  The latter is the preferred method as is doesn't
impose a security login for ALL of their Access files, but only when they
use the shortcut to open your file.