Linking tables in Access with unique ID
Each table should have a UserID column, used to "link", or relate, rows in the User table with rows in the Personal, Business, and Board tables.  

In SQL language, this looks like:

CREATE TABLE Users
(
    UserID int PRIMARY KEY
    , UserName varchar(30)
);

CREATE TABLE Personal
(
    PersonalID int PRIMARY KEY
    , UserID int FOREIGN KEY Users(UserID)
    , PersonalDetails varchar(40)
);

CREATE TABLE Business
(
    BusinessID int PRIMARY KEY
    , UserID int FOREIGN KEY Users(UserID)
    , BusinessDetails varchar(40)
);

CREATE TABLE Board
(
    BoardID int PRIMARY KEY
    , UserID int FOREIGN KEY Users(UserID)
    , BoardDetails varchar(40)
);


Then, when you want to query those tables, you'd write something like:

SELECT UserName
    , PersonalDetails
    , BusinessDetails
    , BoardDetails
FROM Users
    INNER JOIN Personal ON Users.UserID = Personal.UserID
    INNER JOIN Business ON Users.UserID = Business.UserID
    INNER JOIN Board ON Users.UserID = Board.UserID