To make certificates you can go to the Studio and hit 'Certificates'. This is where you'll see an overview of the certificates that are already on the platform. The status of every certificate is visible as well, which can either be published (the certificate is available for use  in a course), unpublished (the certificate still needs to be published before it can be used) or 'validation errors' (Some information in the certificate isn't filled out correctly or completely). On the top you can see there are two tabs; certificates and certificate template. 

To create a new certificate, you can click on the tab 'Certificates' and click the top right button 'New Certificate'. When you fill in the name, expiration date and provide a short description about what the certificates stands for, you can continue to go more in detail.

On the next screen you can select the template you want for this certificate. If you hit 'Add template', you'll have access to all the templates that are already present on the platform. If you want to know how to create your own template, click here).
You can also add a signature from your computer to the certificate, to make it really official. 

An option is that you don't want everybody to just get a certificate after finishing a course, but must complete a quiz before receiving it. On the right pane you can turn 'Certificate Quiz' on. This is where you can then add the questions you want them to solve before receiving the certificate. If you enable the advanced settings, you can even set the quiz pass rate (the percentage a user needs to achieve to pass the quiz and receive the certificate) and set in detail if the students can retry the quiz or not. 

If you finally press 'Save Changes', you just create a certificate! If you actually want to use the certificate, make sure you press the button 'Publish' in the top right corner, so you can start attaching the certificate to the relevant course!