1. If you want to receive payments on your website, you need to contract with one of the payment gateways for which we have a payment plugin and then configure the plugin with the information provided by the payment gateway.
2 and 3. I invite you to read that tutorial
www.hikashop.com/en/support/documentatio...splay-front-end.html
which explains how to display your products on the front end.
Once you created a menu of the type hikashop product listing via the joomla menu manager, you can just set it as default so that it appears on your main page.