Follow documentation to install postgresql if it is not already installed.

Run the command to create the db that you will be using

createdb mydb

Run the command to load the db instance

psql mydb

Create the tables before importing csv files. Please double check the create table statements in case I miscopied them.

CREATE TABLE warehouse (
	W_ID INT PRIMARY KEY,
	W_NAME VARCHAR(10),
	W_STREET_1 VARCHAR(20),
	W_STREET_2 VARCHAR(20),
	W_CITY VARCHAR(20),
	W_STATE CHAR(2),
	W_ZIP CHAR(9),
	W_TAX DECIMAL(4, 4),
	W_YTD DECIMAL(12, 2)
);

CREATE TABLE district (
	D_W_ID INT,
	D_ID INT,
	D_NAME VARCHAR(10),
	D_STREET_1 VARCHAR(20),
	D_STREET_2 VARCHAR(20),
	D_CITY VARCHAR(20),
	D_STATE CHAR(2),
	D_ZIP CHAR(9),
	D_TAX DECIMAL(4, 4),
	D_YTD DECIMAL(12, 2),
	D_NEXT_O_ID INT,
	PRIMARY KEY (D_W_ID, D_ID),
	FOREIGN KEY (D_W_ID) REFERENCES Warehouse(W_ID)
);

CREATE TABLE customer (
	C_W_ID INT,
	C_D_ID INT,
	C_ID INT,
	C_FIRST VARCHAR(16),
	C_MIDDLE CHAR(2),
	C_LAST VARCHAR(16),
	C_STREET_1 VARCHAR(20),
	C_STREET_2 VARCHAR(20),
	C_CITY VARCHAR(20),
	C_STATE CHAR(2),
	C_ZIP CHAR(9),
	C_PHONE CHAR(16),
	C_SINCE TIMESTAMP,
	C_CREDIT CHAR(2),
	C_CREDIT_LIM DECIMAL(12, 2),
	C_DISCOUNT DECIMAL(5, 4),
	C_BALANCE DECIMAL(12, 2),
	C_YTD_PAYMENT FLOAT,
	C_PAYMENT_CNT INT,
	C_DELIVERY_CNT INT,
	C_DATA VARCHAR(500),
	PRIMARY KEY (C_W_ID, C_D_ID, C_ID),
	FOREIGN KEY (C_W_ID, C_D_ID) REFERENCES District(D_W_ID, D_ID)
);

CREATE TABLE "order" (
    O_W_ID INT,
    O_D_ID INT,
    O_ID INT,
    O_C_ID INT,
    O_CARRIER_ID INT,
    O_OL_CNT DECIMAL(2, 0),
    O_ALL_LOCAL DECIMAL(1, 0),
    O_ENTRY_D TIMESTAMP,
    PRIMARY KEY (O_W_ID, O_D_ID, O_ID),
    FOREIGN KEY (O_W_ID, O_D_ID, O_C_ID) REFERENCES Customer(C_W_ID, C_D_ID, C_ID),
    CHECK (O_CARRIER_ID IS NULL OR (O_CARRIER_ID BETWEEN 1 AND 10))
);

CREATE TABLE item (
    I_ID INT PRIMARY KEY,
    I_NAME VARCHAR(24),
    I_PRICE DECIMAL(5, 2),
    I_IM_ID INT,
    I_DATA VARCHAR(50)
);

CREATE TABLE "order-line" (
    OL_W_ID INT,
    OL_D_ID INT,
    OL_O_ID INT,
    OL_NUMBER INT,
    OL_I_ID INT,
    OL_DELIVERY_D TIMESTAMP,
    OL_AMOUNT DECIMAL(7, 2),
    OL_SUPPLY_W_ID INT,
    OL_QUANTITY DECIMAL(2, 0),
    OL_DIST_INFO CHAR(24),
    PRIMARY KEY (OL_W_ID, OL_D_ID, OL_O_ID, OL_NUMBER),
    FOREIGN KEY (OL_W_ID, OL_D_ID, OL_O_ID) REFERENCES "order"(O_W_ID, O_D_ID, O_ID),
    FOREIGN KEY (OL_I_ID) REFERENCES Item(I_ID)
);

CREATE TABLE Stock (
    S_W_ID INT,
    S_I_ID INT,
    S_QUANTITY DECIMAL(4, 0),
    S_YTD DECIMAL(8, 2),
    S_ORDER_CNT INT,
    S_REMOTE_CNT INT,
    S_DIST_01 CHAR(24),
    S_DIST_02 CHAR(24),
    S_DIST_03 CHAR(24),
    S_DIST_04 CHAR(24),
    S_DIST_05 CHAR(24),
    S_DIST_06 CHAR(24),
    S_DIST_07 CHAR(24),
    S_DIST_08 CHAR(24),
    S_DIST_09 CHAR(24),
    S_DIST_10 CHAR(24),
    S_DATA VARCHAR(50),
    PRIMARY KEY (S_W_ID, S_I_ID),
    FOREIGN KEY (S_W_ID) REFERENCES Warehouse(W_ID),
    FOREIGN KEY (S_I_ID) REFERENCES Item(I_ID)
);

Next to prepare your csv files, add these headers in the first row of your csv files:

W_ID,W_NAME,W_STREET_1,W_STREET_2,W_CITY,W_STATE,W_ZIP,W_TAX,W_YTD

D_W_ID,D_ID,D_NAME,D_STREET_1,D_STREET_2,D_CITY,D_STATE,D_ZIP,D_TAX,D_YTD,D_NEXT_O_ID

C_W_ID,C_D_ID,C_ID,C_FIRST,C_MIDDLE,C_LAST,C_STREET_1,C_STREET_2,C_CITY,C_STATE,C_ZIP,C_PHONE,C_SINCE,C_CREDIT,C_CREDIT_LIM,C_DISCOUNT,C_BALANCE,C_YTD_PAYMENT,C_PAYMENT_CNT,C_DELIVERY_CNT,C_DATA

O_W_ID,O_D_ID,O_ID,O_C_ID,O_CARRIER_ID,O_OL_CNT,O_ALL_LOCAL,O_ENTRY_D

I_ID,I_NAME,I_PRICE,I_IM_ID,I_DATA

OL_W_ID,OL_D_ID,OL_O_ID,OL_NUMBER,OL_I_ID,OL_DELIVERY_D,OL_AMOUNT,OL_SUPPLY_W_ID,OL_QUANTITY,OL_DIST_INFO

S_W_ID,S_I_ID,S_QUANTITY,S_YTD,S_ORDER_CNT,S_REMOTE_CNT,S_DIST_01,S_DIST_02,S_DIST_03,S_DIST_04,S_DIST_05,S_DIST_06,S_DIST_07,S_DIST_08,S_DIST_09,S_DIST_10,S_DATA

Copy all of your csv data into your postgres tables, make sure to copy them in order

COPY warehouse FROM 'path/to/project_files/data_files/warehouse.csv' WITH CSV HEADER;

order and order-line table is a little tricky so use this command instead to account for the null values

COPY "order" FROM 'path/to/project_files/data_files/order.csv' WITH CSV HEADER NULL 'null';