Auto Readmore in "Category Widget"

On my homepage, we used a “More” tag to shorten a post on the homepage and have a “read more” link. 
When add a new content,  in the content frame please put the cursor in anywhere you would like , and click on “More” button.
Please take a view below:

Or you can use this plugin to automatically shorten: Easy Custom Auto Excerpt
Regards,

Hi there,
I know the button to add, but unfortunately that is always forgotten.

I’ve also tested some plugins, but the function does not seem to work in widgets.
I have now installed and enabled Easy Custom Auto excerpt, but in the widgets nothing happens.

My problem is that my home page just does not look nice because the lyrics are too long and I want that it will be adjusted automatically.
You can see it on: test5.gec-ritter.de
 
regards,
Ben

To resolve this issue, you only possible log in to Dashboard > Post > Edit post, then add the content to the Excerpt section.
See the screenshot: http://prntscr.com/47f2fk
If you not find the Excerpt section, you can open the Screen Options on the top side then select the Excerpt check-box.
See the screenshot: http://prntscr.com/47f31g
Hope this helps !