How to add a category link to navigation menu?

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Hi,

what is the easy way to add a working category link in my navigation?

When I look at my demo navigation I see this links

<p class="groupdrop-title">SERVICES</p>
<ul class="groupdrop-link">
<li class="item"><a href="http://domain.com/admin_yasgdsdi/cms/wysiwyg/directive/___directive/e3tzdG9yZSBkaXJlY3RfdXJsPSd3b21lbi90b3BzLXdvbWVuLmh0bWwnfX0,/key/97d5b77ca87038c395f3735af7e9bac5205a1ad2b086ad988a77131913ab802d/">Shop &mdash; Catalog</a></li>

How can I add my own links to a specified category?

Is there any button in the wysiwyg editor which I didn't find?

thank you

regards