If you are running the cloud/online version of Microsoft Dynamics 365 Business Central, you can find and install the Commerce 365 for Magento app in Microsoft AppSource.
Click on ‘Free Trial’ and follow the steps presented by Microsoft AppSource which will guide you through the technical installation.
If you directly want to install both the core extension and the B2B module, then follow this link to install the B2B module, which will automatically install the core extension as well.
Once the installation of the extension is finished, in Business Central, go to My Settings by clicking on the gear icon in the top right corner, and switch to the Commerce 365 Manager role. This will take you to the dashboard which is the best starting point for further setup & configuation.
The dashboard will automatically detect that the extension is installed, but not yet configured. Click on the link next to the notification to start the setup wizard.
You can always go back to the role center screen and start the wizard again by clicking on the Setup Wizard action button. And, the same values can also be altered by going to Administration > Setup.