To set up a minimum order quantity for a product in Magento 2, log in as the admin and open the product for which you want to set up a minimum order quantity.

The following steps are:

1. Click on 'Catalog' and then click on 'Products'.

2. Click (or search by keyword) the product you wish to customize. 

3.  Click on 'Advanced Inventory' to proceed.

4. Here you can choose the amount of the minimum order quantity that the customer must order, which you can type in the 'Minimum Qty Allowed in Shopping Cart' field. Then click on the 'Done' orange button.

If the customer selects a number that is lower than the minimum order quantity, a notification will be shown on the product page.

5.  After clicking on 'Done', you will have to click on the 'Save' button to save your changes and then you will be done!