Can someone please explain this to me?

It's basically saying that the things we imagine are based off things we aleady know.

For example, if we imagine a giant purple bird flying over a cloud, this is based off what we know. We know what a bird is, we know what a cloud is, and we know what giant looks like and what purple looks like.

Knowledge comes from experience. Our experiences remain in our memories.

So when we dream up poetry, we are taking ideas from the things we remember about our own lives.

My translation of what it COULD mean:

It can be said that memory is the basis of poetry, because imagination is an example of poetry. We know the answers to our imagination already. The ability to imagine comes from our memories of what we experienced in life so far to use on a different situation.

Basically poetry is based on our memories that we've had in life, or what we have already experienced. We just use that "poetry" to apply it to other situations that come before us.

I guess the lines u could not understand mean- Our memory is the birth place for every poetry. As when we try to imagine something at that time we usually make our brain work hard so that the memory could bring out the best imagination for us to create a nice poetry... I don't know how much it really expresses the meaning of the lines. I've tried my best... Thank you...