Welcome to Android Central! Unfortunately, not all app developers adhere to Google's app guidelines (which typically include having a "hamburger" menu icon at the upper left or upper right). This can especially be evident when an app is clearly just a port of an iOS app. In these cases, you just have to look closely for some other way to access the settings. Look for some variant of a hamburger menu icon (i.e., 3 horizontal lines), or an icon that looks like 3 dots in a vertical column or horizontal row.
If this is the
Studio Clock app you're talking about, the Menu button is the 3 vertical dot button right next to the nav buttons.
Happy New Year!