To Install and Configure Omnisend, Go to Settings - > Click on Integrations and Click on Connect.
Next is to add the Private API key.
To get your API keys, Login to your Omnisend Account -> Go to store settings -> Click on Integrations and API -> Click on API keys -> Create API Key -> Copy API Keys and Enter the Keys on the 99minds platform and Click on Save.
Click on Integrations and you will now see that you have configured the app.