I read that teacup should be installed with my tclsh but i can not find it. I am using 8.6.
Teacup is no longer supported.
The last version we built that provided support for TEA was 8.6.5. At that point, we stopped releasing versions of Tcl that were significant forks away from the reference versions. The reference versions do not support TEA.
How do i access its packages then? Also on 8.5 i tried installing the Tkhtml package with it and it said it couldn’t find it.
Your 8.5 version might be too old to be usable. Many of them are, because they can only use SSLv3 or lower, which is routinely blocked now.
Packages are added to our current Tcl 8.6 releases during the build process. If the Featured Project doesn’t have the modules you want, the method is to fork a copy of it and customize the content. (See the help page for how to use The Platform for builds.) However, there are not a lot of Tcl modules available. Most of what we have is already in the Featured Projects.