Don't worry the categories are there. They just won't show up until there is a post in the caertogy.The other possibility is that you don't have the categories widget in your sidebar. You can go to Appearance / Widgets and drag the categories widget to your sidebar.
Top Categories
Recent changes
MattisManzel • 4 hours ago
Frullatore • 15 days ago
2601:647:CD01:DE50:0:0:0:E4BC • 1 month ago
Lw'z Dab • 2 months ago