Assuming the connector has been configured correctly (otherwise please follow these steps), you should be able to create your Lead object as a Synchronised Data Extension, in Contact Builder > Data Sources of the Business Unit where the connection has been established:
- Select the data source connected via account integration on the Synchronized tab.
- Click Set Up Object.
- Click Synchronize for the entity containing the data to bring into Contact Builder.
- Select the checkboxes next to the fields to synchronize and click Next.
- Choose whether to bring in all records or begin at a certain date using the Records Collection buttons.
- Choose how often you wish the synchronize data in the Poll Schedule dropdown menu.
- Click Save & Synchronize.
Find recommended best practices for Synchronised Data Sources in this document.