Roughly like below. You may have to adjust the "SINGLE_NCLOB" to "SINGLE_CLOB", depending on the format of the input file.

DECLARE @file_text varchar(max)

SELECT @file_text = file_text

FROM OPENROWSET(BULK 'd:\full\path\to\file\filename.txt', SINGLE_NCLOB) AS file_bulk(file_text)

--(Or)

--INSERT INTO dbo.tablename ( file_name, file_text )

--SELECT 'File1' AS file_name, file_text FROM ...

SELECT @file_text