To be able to get the answers from the linked question working with the given editor on www.tutorialspoint.com and producing the desired result, you have to do some small modifications.
The answers by @Qrrbrbirlbel and @m0nhawk are using the standalone document class. As the corresponding class file - namely standalone.cls - does not seem to be available with the TeX Live 2016 installation used by your online editor, you have to switch to another document class. The easiest solution would be to use the article class:
\documentclass{article}
\usepackage{tikz}
This has to replace \documentclass[tikz]{standalone} in the answer by @Qrrbrbirlbel and the first two code lines of @m0nhawk's answer.
@Toscho already uses the article class, but you pointed out that your wheel should be clockwise. One easy way to circumvent this is by replacing
\node at (\x*360/26+360/26+180/26:6){\Alph{encrypted}};
\node at (\x*360/26+360/26+180/26:8){\Alph{original}};
with
\node at (-\x*360/26+360/26+180/26:6){\Alph{encrypted}};
\node at (-\x*360/26+360/26+180/26:8){\Alph{original}};
The article class is normally used for regular documents which should be typeset in A4 format for example. Being one of the standard document classes, it should be available on most systems.
The standalone class produces a document whose dimensions are only as big as needed by the content - and is often used to create complex images as standalone PDF files to be included later into a normal document without requiring to typeset this image on every compilation run for the main document. As it is no standard class, it might be missing in some installations.
\documentclass{...}and ending with\end{document}. – Andrew Uzzell Dec 11 '18 at 15:15\documentclass{article}instead of\documentclass[tikz]{standalone}(where the document class file is missing for some reason) and loading thetikzpackage afterwards with\usepackage{tikz}should do the trick. For the other example, you may use\node at (-\x*instead of\node at (\x*as a simple solution. – epR8GaYuh Dec 11 '18 at 15:17