Mentioning is available for LinkedIn Company Pages (to company pages), LinkedIn Profiles (to company pages), Twitter (to all users), and Facebook Pages (to pages). Mentioning on Instagram has to be done when creating the post inside Facebook Creator Studio.
Step 1. Visit your Social posts page and create new social posts via the button located at the upper-right, or open existing posts via the Edit link.
Step 2. Choose which channels to publish and create the master message (located to the right of channels).
Step 3. In the Tailor by channel section, you are able to mention other people and companies.
LinkedIn Company Pages and LinkedIn Profiles
Just type @ followed by the name of the page. Only pages with over 300 followers can be mentioned.
Start with @ and type the username, or search using actual name or topic. For example, if you begin with @football, you will receive a list of football teams.
To mention a page, first like it using your page on Facebook. Then you will be able to type @ to mention them.