I created this table called LOCATION by doing this:
CREATE TABLE LOCATION(
POSTCODE VARCHAR(10) PRIMARY KEY,
STREET_NAME VARCHAR(20),
CITY VARCHAR(20));
You're missing quotes around the first value, it should be
INSERT INTO LOCATION VALUES('PQ95VM', 'HAPPY_STREET', 'FRANCE');
Incidentally, you'd be well-advised to specify the column names explicitly in the INSERT, for reasons of readability, maintainability and robustness, i.e.
INSERT INTO LOCATION (POSTCODE, STREET_NAME, CITY) VALUES ('PQ95VM', 'HAPPY_STREET', 'FRANCE');