SQL Server :: Calling A Trigger After Insert Sp?

i want to create a trigger after i insert record in table1 and in trigger there will be an update sentece which updates x column in table2 so i have a stored procedure like insert into Table1(a,b,c) values(1,2,3)select @@identity then my trigger should update table 2 update table2 set x=5 where id=@a @a parameter must come from my insert stored procedure's select @@identity line how can i create a trigger like this? this will be my first trigger so i dont know anything about them after creating trigger i think i should control if it execute successfully or not in my insert stored procedure so if it works successfully my insert is ok but if trigger doesnt work my insert sentence shouldnt work