Your julian goes into the DATEJUL function and is converted to a SAS numerical date stored in the JULDTE variable. The PUT function loads the JULDTE variable into the YYMMDD format and is now loaded into variable YYMMDD.
For input, use JULIANw. or PDJULw. (if packed) format to read in the Julian date. Then use a FORMAT varname YYMMDD6. ; to output as YYMMDD6. format. SAS dates are stored as an integer number of days since January 1, 1960 and can be output as desired by using the FORMAT statement.