A kenning, as you illustrated in the example in your question, is a poetic renaming or redescribing of the subject. Sometimes the kennings in Beowulf really jump out at the reader, sometimes they're harder to recognize, and sometimes it's just hard to tell whether or not something qualiifies as a kenning.
The second paragraph in Chapter 1 has at least four examples of kennings:
There was Shield Sheafson, scourge of many tribes,
a wrecker of mead-benches, rampaging among foes.
This terror of the hall-troops had come far.
A foundling to start with, he would flourish later on
as his powers waxed and his worth was proved.
In the end each clan on the outlying coasts
beyond the whale-road had to yield to him
and begin to pay tribute. That was one good king.
The exact phrasing will vary, of course, based on the translation that you're using. I'm using Seamus Heaney's translation. (The link to the opening to Book 1 is given below.) Kennings in this one paragraph include:
scourge of many tribes
a wrecker of mead-benches
This terror of the hall-troops
the whale-road (= the ocean)
I would encourage you to identify your own set of favorites (I really love that idea that "a wrecker of mead-benches," which might be rephrased today "a bar-room brawler," makes a good king!) If possible, pick and discuss examples from different parts of the poem.