Depending on what skyrim version you want to mod you will need different creation kit versions. I myself use skyrim SE 1.5.97 and I will explain everything for this version. If you do not have this version you can install the most recent one, download skyrim downgrader from nexus and bring it back to version 1.5.97. Link is underneath.

https://www.nexusmods.com/skyrimspecialedition/mods/57618

I use this version because it is stable, most mods are based on this version and everything that is recently being added can be implemented sort of as a mod already.

If you do have skyrim se version 1.5.97 then you have a major problem right now. The recent creation kit (ck) is not compatible with your version. Go to steam, install the creation kit (for the sake of being able to launch it).

I found the latest skyrim se 1.5.97 version in the archives with the help of a Redit post. You can use this file to overwrite the ck from Steam. I am putting the ck file in attachment. You can simply extract the file and place them in you game folder under Program Files (x86) like shown in the image.

Your second issue starts right there. This version of the ck is unstable and requires certain fixes from other mods to make is usable.

The first fix you need is the from this mod: https://www.nexusmods.com/skyrimspecialedition/mods/20061 (CK64Fixes Release ...)

You can install this by following the instructions as given by the mod creator. (Just download the file and extract in the same place as your ck)

Optional You can also install FaceFXWrapper (0.4) but this is optional. If you don't install this (or incorrect). You won't be able to hear the voice lines in you ck or generate lip sync to sound files but thats it. It won't affect you once you are playing.

However CK64Fixes is outdated an no longer works on its own.

You can find the upgrade version in this link: https://www.nexusmods.com/skyrimspecialedition/mods/71371?tab=description

Instalation instructions are again provided by the modder. (Just dowload the file and extract in the same place as your ck, let it overwrite CK64 Fixes Release files)

If everything went well, you now have a smoothly working ck that won't crash on opening it. ?

Creation kit 1.5.97.7z