How Do I Use the 'description:ellipsis'?

Its about this code:
[[+description:ellipsis=’50’]]
Adds an ellipsis to and truncates a string if it’s longer than a certain number of characters. Defaults to 100.

Where do I put this to make it work?

I already tried to substitute it with [+summary+] on the article page layout but nothing happened

Or maybe in this this chunk ?

[tt]:ellipsis[/tt] is an output filter for MODx Revolution (2.0.x).

It looks like you are using Evolution. I assume that because you write [+summary+].

In Revlution you can use [tt]:ellipsis[/tt] everywhere where you output content, i.e. in templates or chunks.

BTW: this is not the right forum for your question. This one is about "Module, Plugin & Snippet Creation and Modification". You should rather have asked in "General Support".

When using the summary extender you can also use the &truncText parameter.

Pur: Text to be displayed in [+link+]
Opt: Any valid text or html
Def: ”Read more...”