There is no way to bypass the certificate step, since you need a certificate for the Skype for Business services to start.
Adding the Certificate Authority role to a server is fairly straightforward.
Since this is a lab environment (assuming you have a domain controller, and a domain to which you've joined the SfB server), I would suggest installing the CA role on your domain controller. Here is how to do so:
In Server Manager, click manage, then Add Roles and Features. Click next until you get to the Server Roles screen in the Add Roles and Features Wizard.
From there, select Active Directory Certificate Services and click next. The wizard will guide you through setting up the CA role on your machine. You do not need to worry about making it an enterprise CA, since this is a lab environment.
Once that is setup, you can run Step 3 of the SfB Deployment wizard, and request a certificate from your online CA, and assign it.
From here, you should be good to go.