If you installed via F-Droid then you just have to wait some time. If you want to get 0.18.0 right away then download it here: https://github.com/TeamNewPipe/NewPipe/releases
If you download the app from GitHub you will get notified of updates.
No.. No.. I talk about In app Update for without going anywhere like Facebook. With out use Google Play Service
So I find on Google for this function but more Confusing. To this please support for Simple but Confusing problem🤔🤔
Do you see the updates section like in the screenshot below? If not then your have the fdroid version of the apk and you will have to download the apk from fdroid only.

》》I compare both versions so f-droid version not showing update btn like ^^ this image but github version Showing this button . So learn this concept of notification on open newpipe app. What code works in Update btn showing notification on update is available... and Go to Link on click Notification Go to new version link of Github
》》 github.../newpipe0.18.apk
Because I clone this newpipe 0.17.4 app code and I make Release Version of this App Code Bundle . So this btn nI learn about this Function so many helpful For My Other Apps. 😀😀😀
I'm closing since the question has been answered (no) and it won't be implemented (see https://github.com/TeamNewPipe/NewPipe/pull/3141)