To connect Fusion to Chartio, make sure you have created your Fusion account.
Then login into Chartio. Click Add Data Source and select MySQL as shown below.
Plug in your Fusion warehouse credentials then click Connect.
Select import for the tables you want to include. Then click Apply.
Then to add foreign keys, go to the Schema tab.
Then connect your fused tables via the corresponding links table. For example, if I want to connect Fused Activity to Fused Contact, I will need to add the foreign keys Activity Id and Contact Id via the Links Activity Contact table, as shown below:
Repeat this process for any tables you would like to join together and you should be able to see the tables on the Chartio canvas when you add Dimensions and Measures for both. Otherwise, tables without a foreign key connecting them will be grayed out, as shown below: