I need to write a journal entry about the first chapter in The Lion, The Witch, and the Wardrobe.

I think that there are different approaches that can be taken
with a journal entry. If there are specifics that have to be followed, I would pay attention to
these before anything else. The entry might be designed to extract a response from you about what
has been read in the first chapter. If this is so, then it is fairly open ended. You could write
about how Lewis has established the opening, or exposition, of the novel. Perhaps, another strand
of thought that can be explored is your impressions of the characters in the initial chapter.
Discussing their traits or their early motivations might be something about which writing can be
done. Discussing the stepping through the wardrobe might be an entire response in its own right.
It is not lost on the reader that the setting is Britain during World War II. The presence of
evil in the world can only be escaped through a wardrobe. Discussing the implications of this in
a response could be quite fascinating and worthwhile.