This is certainly a rather confusing poem in lots of ways, as it defies any kind of meaning that we would try to impose on it because of its fantastical nature, so I am not surprised you are struggling to understand it! I will provide you with a summary of the poem that will hopefully enable you to gain a basic understanding of what the poem is talking about so you can begin to perhaps understand it.
It is important to remember that Coleridge apparently experienced the vision of what he writes about during an opium-inspired dream, and then woke up and wrote down the experience in this poem. This may explain the strong visual element of this poem. The speaker states that Kubla Khan has built a majestic pleasure dome in Xanadu, with gardens, forests and winding streams. Artificiality (man-made creation) and nature sit side by side, and deep in a chasm a fountain bursts forth, which sends the sacred river Alph into a motionless ocean. Alongside the voice of this river, the Khan, we are told, hears voices that predict war.
The next stanza then shifts to a vision of an Abyssinian woman playing a dulcimer. This inspires the speaker to try to recapture her music and through this re-create the pleasure dome at Xanadu, which would inspire awe and fear in people as they marvel at the speaker's act of creation.
Hope this helps! It is a complicated poem, but the rhythm and use of alliteration make it a very easy poem to memorise.