Where is headerinclude with {$stylesheets} located ?

[LittleFoxy]

I recently installed the MyFontAwesomeIcons FA4 plugin and in the plugin tutorial page (https://community.mybb.com/mods.php?acti...w&pid=1259) it's written that I must find the headerinclude template and make sure that after 

{$stylesheets}

I need to find 

<link href="{$mybb->asset_url}/inc/plugins/myfontawesomeicons/font-awesome/css/font-awesome.min.css" rel="stylesheet" type="text/css">

But I don't know where this is located ?

[SvePu]

You can find it under theme template group "Ungrouped Templates"

[.m.]

see also this => templates related guidance