An easy way is to check their log files in each user's HOME directory. This is only for LID login in and does not work for PORTAL login. Also check out each user's job log or print directory if you want to see the last time a batch program was run by that user.
For Portal login, it will be more difficult. Unfortunately 8.0.3 Lawson does not provide a one-stop shop for reporting who and when a Portal user last logged in. If your Portal resides on a Windows server, you might want to try looking at the log files stored there: logan.log, and IOS.log. Also you might also want to try turning on logging at the OS level to log each time a user accesses or logs into that Windows server which is what in effect they are doing when they log into Portal.