You need to add new datafile to your SQL SERVER that has LOGSHIPPING. So automatically same datafile will be created on secondary side. What if drive letter is different on secondary node?
To manage you sould run this command on secondary side to tell sql server to create datafile on where you want.
ALTER DATABASE DB_logshipping FILE (NAME = new_addedfile, FILENAME = 'E:\Program Files\Microsoft SQL Server\MSSQL\DATA\new_addedfile.ndf')