The exact details depend on your database design and what timestamp value you want to enter (Current timestamp? a Value entered by the user?)
Go To Layout [//Specify layout of table where you want a new record unless you are already on that layout]
Set Field [YourTable::YourTimeStampField ; Get ( CurrentTimeStamp) ]
If YourTimeStampField is set up to auto-enter the creation time stamp, the last line of the script will not be needed as this value will then be entered automatically when the record is created.
You can even do all of this without a script in many cases. If you set up a portal to a related table where you want your new record, for example, all the above can take place just by entering data in the bottom blank row of the portal--provided "Allow creation of records..." is enabled for the portal's relationship.