Shop information must be configured.
Depending on whats done with magento might need marketplace.magento.com user to get access tokens for composer. Instructions: https://devdocs.magento.com/guides/v2.4/install-gde/prereq/connect-auth.html
Copy app folder into magento root folder. Continue with terminal commands.
composer require mijora/omniva-api
php bin/magento setup:upgrade
php -d memory_limit=2G bin/magento setup:di:compile
php -d memory_limit=2G bin/magento setup:static-content:deploy --language lt_LT
php -d memory_limit=2G bin/magento setup:static-content:deploy --language en_US
php bin/magento cache:flush
Stores -> Configuration, select Sales -> Shipping Methods / Delivery methods -> Omniva
Fill in all the required information.