Updating the plugin can be done in two ways.
The first option is to go to your account page in OIMWC. In there you will find an update button if a new version exists. It will say “Install Update Now [version number]”
The next option to update the plugin is the normal way all other plugins are normally updated.
In the left admin side menu, you will find “Plugins” and then “Installed plugins”.
Search for “Order and Inventory Manager for WooCommerce”.  Under the title, you will find the text “Update Now” with a light yellow background color. Click on that link to upgrade the plugin.