I am running an Procedure,How can we see the run time of the Procedure ?
For answering what question?
There are different methods to measure it. Like using SQL*Plus's timing feature (as explained above by <i>SomeoneElse</i>). Or by using DBMS_PROFILER. Or DBMS_TRACE. Or using custom instrumentation. Etc.
But without knowing what question you want to answer by determining the execution time of a procedure, it is hard to make a meaningful suggestion.
PS. Run-time has a different meaning than elapsed execution time (which you are actually referring to). Run-time is used to describe the period and context during which a process is executing. It is also more formally called the process life cycle phase. This is different than the time it took for the process to complete its life cycle- to which you are referring.