Using session value in Trigger in SQL Server

How can we use session value in trigger in SQL Server 2012 and insert into a table? I created a session but getting confuse, how can i use session value into a trigger. I'm creating a log table for view all logs that which action is acted in main table and also know how can I get ID in where condition while I update data using update trigger ? Plz let me know about all this...

CREATE TRIGGER EpaperTrgrUpdate
       ON EPaper
AFTER INSERT
AS
BEGIN
       SET NOCOUNT ON;
 
       DECLARE @EpaperId INT
	   DECLARE @Date datetime
	   DECLARE @ActionBy nvarchar(50)
	   DECLARE @Action varchar(50)
 
       SELECT @EpaperId = EPaper.SrNo, @Date = date, @ActionBy = EPaper.ActionBy      
       FROM EPaper
 
	   IF UPDATE(IMG)
       BEGIN
              SET @Action = 'Image Updated'
       END
 
       IF UPDATE(Date)
       BEGIN
              SET @Action = 'Date Updated'
       END

       INSERT INTO Epaper_Log
       VALUES(@EpaperId, @Date, @Action, @ActionBy)
END

Here ActionBy data I want get from session. in normal table I can insert or update session value, but i'm getting how can I get session value in trigger.