Hi there...

There are two ways:

at sqlplus you can type in:
sho parameters
or show parameters

or you can use the v$parameter view by either selecting * from it for all or if you are looking for a particular parameter, then use the where clause for name (name here is the name of the parameter, e.g. db_block_buffers, and remember to put it in correct case and in quotes... the value is the entry.. etc..) just do a desc of V$parameter.

Good luck,
Nirasha