Get to run a theme

I downloaded the kirby plainkit and put it on mamp to test it.
Everything worked.
Then I downloaded a free theme, I deleted the plainkit folder and replaced it by the themefolder.
It did not work.
The same I tried to do with a bought theme. it did not work also.
Do someone know why it is like this .
Is there something I do not check?
Do I need to buy a licence before runing a theme?
Would be nice if someone can give me a kick:)

I don’t know what your themes contain. Often, a theme comes as a complete Kirby installation, ready to run.

Other themes leave out the /kirby folder. Then you would have to download Kirby from GitHub and put it into the theme folder.

Maybe you can post the folder structure of your theme?

Does it make a difference, weather I Download it from github or from the official get kirby website?

I themes I talk about are the “Zeta theme” and the “Lemmon portfolio theme” .
Thank you Sonja for your answer.

If you download from the getkirby website, you get either the Starterkit or the Plainkit.

If you only need the kirby folder, you better download from GitHub:

Well, I don’t know any of these themes, so cannot tell what they contain.

I just had a look at the Lemmon theme’s readme. For this theme to work, you have to run composer as described in that file. This will automatically install Kirby and other dependencies. If you don’t have composer on your system, you either need to install it or you have to add Kirby and other dependencies manually (just adding the Kirby folder won’t help, because the theme also uses some Twig templating instead of the standard PHP templates).

If you are not familiar with Twig, then maybe the theme is not that useful.

As for the other paid theme, you probably best consult the instructions first.