You are currently using Exclaimer Cloud - Signatures for Exchange to apply signatures to your emails and now you want to migrate to Exclaimer Cloud - Signatures for Microsoft 365.
The procedure you follow depends on your initial setup and whether you had Microsoft 365 in place when you first configured the Exclaimer Cloud product.
If you choose to set up both features: Setup for Microsoft 365 Exchange Online Service and Setup for On-Premises Exchange Server then you don't need to do anything - as your emails will already be routing to Exclaimer Cloud via the Transport Rule and Connectors in Microsoft 365.
If you notice that your signatures are not being applied then please check the conditions of the transport rule as described here: A signature is not applied for one or more user.
If you had no Microsoft 365 infrastructure when you initially configured the product then you will need to set up the Transport Rules and Connectors. For more information, see how you can re-run the Microsoft 365 connector setup.