Follow the below steps to install and set up PWA in 2.3 :

Prerequisite :
You must have a version of  NodeJS >=10.14.1 , and Yarn > = 1.13.0. I suggest using the Latest versions of both are recommended.

1 ) Use the following command :

composer create-project --repository-url=https://repo.magento.com/ magento/project-community-edition /var/www/html/m23

/var/www/html/m23 is a Magento installation directory.

2 ) Install Magento by Command Line:

php bin/magento setup:install --base-url=http://localhost/m23 --db-host=localhost --db-name=nik_m23 --db-user=root --db-password=webkul --admin-firstname=John --admin-lastname=Doe --admin-email=test@webkul.com --admin-user=admin --admin-password=admin123 --backend-frontname=admin_magento --language=en_US --currency=USD --timezone=Asia/Tbilisi --cleanup-database --use-rewrites=1

While you have completed with Magento installation, Now
3 ) Now clone pwa-studio repository :

https://github.com/magento-research/pwa-studio.git

git clone https://github.com/magento-research/pwa-studio.git

I have cloned this repository in magento root directory ex: /var/www/html/m23
4 ) You will see the pwa-studio directory in /var/www/html/m23.
Enter into this directory :

cd pwa-studio/

5 ) Run :

yarn install

6 ) Specify the Magento backend server in .env file. you can see the .env.dist file in
/var/www/html/m23/pwa-studio/packages/venia-concept/ direcoty. If you are not
able see, enable show hidden files. Now create .env file from this env.dist

cp packages/venia-concept/.env.dist packages/venia-concept/.env

7 ) Open this .env file and find MAGENTO_BACKEND_URL. Here configure your
local Magento 2.3 instance, my case it is :

MAGENTO_BACKEND_URL="https://magento2-pwa.com/"

7.1 Generate SSL certificate because PWA features require an HTTPS Secure Domain. From the root directory of PWA (/PWA-studio) run the below command:

yarn buildpack create-custom-origin packages/venia-concept

Note: 7.1 Feature requires administrative access.

8 ) Now let’s install sample data for venia-theme to make it good-looking.

9 ) Run the following command in the Magento root directory setup the repository for the sample data in https://repo.magento.com: composer config –no-interaction –ansi repositories.venia-sample-data composer https://repo.magento.com

9 )  Require in the sample data :

composer require --no-interaction --ansi magento/venia-sample-data:*

10 ) Now go back to pwa-studio directory /var/www/html/m23/pwa-studio and start Server.

yarn run build

The above command maybe gives the permission error, so run the below command with sudo.

sudo yarn run build

12 ) Run the server, Use any of the following commands from the project root directory to start the server:

yarn run watch:venia
yarn run watch:all
yarn run build && yarn run stage:venia

Last steps to run the following commands :

bin/magento setup:upgrade 

bin/magento indexer:reindex

bin/magento cache:flush

You are Done! 🙂