It is actually very easy to make certificates using Microsoft PowerPoint. There are plenty of templates you can choose and modify.
1. Choose Design and Orientation, either you want it to be Portrait or Landscape.
2. Choose Font/s and Size/s, you can BOLD to highlight name, certificate name, etc. Design the certificate, e.g. text alignment, you may as well insert your logo, etc.
* Save a master copy, so you can re-use it for other names and certificates. Save as PDF if it is an e-certificate. Avoid full-color background so certificates can be easily printed out by holders.
Samples: