Sure, you can use Cloudflare along with our hosting, with a few caveats.
In order to add your domain to our hosting, you must update the nameservers of your domain to do so. Note that this is only necessary for the initial setup, once the domain is added you can change the nameservers back to Cloudflare.
The other caveat is that you cannot do this if your registered your domain with Cloudflare, because they don’t allow you to change the nameservers of your domain. We’re aware of this and are looking to add an alternative verification method, but until then you cannot host domains here if they are registered with Cloudflare.