Hello Mustapha,
You can check the validity of *LOAD_BLAST_ENHANCED using the following formula:

See the LS-DYNA user manual vol I for more details.
To use *LOAD_BLAST_ENHANCED in WB LS-DYNA, you can create a command snippet:

To specify the faces of the structure where the blast load will be applied, you can create a named selection with an ID:

Let me know if this helps or not.
Reno.