How do i set the default value for any area using SQL in MS Access?

I attempted this but got a syntax error:

CREATE TABLE HELLO
( MUN INTEGER  NOT NULL,
ADD   CHAR(50) DEFAULT'16 asd ST.'
)

The term ADD is really a keyword. Do this:

CREATE TABLE HELLO
( 
    MUN INTEGER  NOT NULL,
    [ADD] CHAR(50) DEFAULT '16 asd ST.'
)

The DEFAULT and CHAR key phrases are just supported much more the ACE/Jet engine's ANSI-92 Query Mode (after which only in SQL DDL). As Jose Basilio highlights, ADD is really a reserved word and should be steered clear of using square brackets. Also, you'll need a space between your DEFAULT word and it is clause (as Jose has proven).

If you're performing the SQL inside a Query object within the MS Access interface you will have to vary from the default (ANSI-89 Query Mode) to ANSI-92 Query Mode. See: About ANSI SQL query mode.

If you're creating the table programmatically e.g. you're using DAO then use a CurrentProject.Connection.Execute "Sql goes here" where CurrentProject.Connection is definitely an ADO classic or any other OLE DB link with your computer data source.

P.S. Surely you desired you column to become HELLO.Mum :)