How tu put/read a composite type in a table?

Thanks to those who will have the force read my mail until the end ...

I 've search for a long time (one week) how to work with composite type.

create table compositeDef ( i int4 , t text ) ;
create table myTable ( j int4 , c composite);

I'm right (isn't it?) because when i create a naw table , a new type is
created automatically ?

But i don't know how i can put (and read) a object of type
"compositeDef" into the table "myTable" ?

Maybe some of you , are thinking it's more easier to create the table
myTable with :
create table myTable (j int4 ) inherits (compositeDef) ;
but it's not the solution i need.

PLEASE HELP !!! : i'm french and i'm a newbie : nothing which is good
for me !!!