First of all, I'm fairly new to Mathematica and the Wolfram Environment in general. If this question has already been asked I'm sorry for the duplicate, but I haven't been able to track down the issue with searches on this site and the web.

I downloaded the AddOn-Package 'Theorema' and in the installation instructions it says that the package can be moved "into one of the locations for standard add-on packages'. In the AddOn folder that comes with the Mathematica installation there are three subdirectories: Applications, ExtraPackages and Packages. Not knowing where to put the Theorema package, I just pasted it into the Packages folder as stated in the installation instruction.

The problem now is, when I open a given .nb notebook file it immediately gives me an error that

the stylesheet TheoremaCore cannot be found by the Wolfram System

even though I have checked and it exists within the Theorema folder.

The second problem is the 'execution' of the Theorema package. The installation instructions say:

...execute the first command in the notebook Needs["Theorema"] by placing the cursor into that cell and hitting Shift+Enter.

However nothing happens when I do that. I also don't know exactly what is meant by "cell".

I hope someone has some kind of advice, thank you in advance.

• Put it in FileNameJoin[{$UserBaseDirectory, "Applications"}] and run Needs["Theorema"], notice the backtick after a. – Kuba Nov 15 '18 at 20:19 ## 1 Answer You should not modify the $$InstallationDirectory$$ of Mathematica. Put it in $UserBaseDirectory instead.

Evaluate

SystemOpen@FileNameJoin[{\$UserBaseDirectory, "Applications"}]
`

to get to the correct location.

The directory structure must look like this: