How to write stored procedure?

I am learning how to write a stored procedure. I kinda get it but I don't.I know it goes something like this..

CREATE PROCEDURE|PROC <sproc name>[<parameter name> [schema.]<data type> [VARYING] [=<default value>] [OUT[PUT]][READONLY][,<parameter name> [schema.]<data type> [VARYING] [=<deafult value>] [OUT[PUT]][READONLY][,...  ...   ]][WITH   RECOMPILE|ENCRYPTION|[EXECUTE AS{ CALLER|SELF|OWNER|<'user name'>}][FOR REPLICATION]AS<code> | EXTERNAL NAME <assembly name>.<assembly class>.<method>

So what I am stuck on and I am trying to understand is this.. Write a stored procedure that accepts a Territory ID, Territory Description, and Region ID and inserts them as new row in the Territories table in Northwind.

Ok so I know I could do something like this I believe:

USE NorthwindGOCREATE PRO spTerritoryASSELECT Territory ID,Territory Description,RegionIDFrom dbo.Territories

But then I can be wrong. But I dont know where to insert then as a new row in the table. I know I would use something like @newrow or @rows along that line. If someone can help me understand who to do a sproc I would be greatful.