I have done that on my own Wordpress website.
You can add this code block to your page.
<form method="GET" action="https://[communityURL]/search" target="_blank"> <input name="query" placeholder="Search the community..." /> <input type="submit" value="Search" /></form>
Make sure to replace [communityURL] with your own URL (e.g community.yourwebsite.com)
This will open the search in a new window. If you want the search to happen on the same tab, you can remove target="_blank".
The result is not styled and will adopt your own CSS.
