OK so I'm looking at your diagram and I'm a bit confused by the lines crossing int he middle. I'm assuming that's the coax coming in and it's not actually splitting to all of those rooms right?
You need the filter only on the entry part of your coax network. It's there to prevent the MoCA signal from escaping your house and heading down the street(can cause problems) if you are using a comcast router with Coax already in it, it probably already had MOCA on it, so you can check check you might already have the filter on your coax setup. Once you know that for sure, as long as your other connections are hitting a MoCA compatible splitter(there are some that apparently don't work but again you have comcast there's a good chance they are already compatible). At each point you will need an adaptor to convert the signal, looks like that's shown pretty well in your diagram. Also your comcast router/modem, like others have said probably has MOCA on it, you will likely need to login to your modem/router and turn it on. If you are using an app to configure it and don't see the option, make sure you check out the actual modem/router webpage which will be accessible at your default gateway address.
Make sure you do not put a filter anywhere but at the houses coax entry point, it will mess up your network.
There are different types of MoCA adaptors, 1.0 which has about 250Mbps, 2.0 I think is 600Mbps, 2.0 bonded 1Gbps, and 2.5 which hits 2.5Gbps. You're router if you are using that likely doesn't have 2.5 but likely does have 2.0 bonded. Don't quote me on the speed for 1.0 and 2.0. Don't get Deca adaptors.
