How can I shrink the transaction log file (.ldf)

Before this make sure there are free entries by setting the recovery model to simple or backing up the log. 

Enterprise Manager:

Right click on the database, All tasks, Shrink database, Files, Select log file, 

Click OK.

t-sql

dbcc shrinkfile ([db_log_name]) Here [db_log_name] is the logical name of the log file as found from 

sp_helpdb or the table sysfiles