Answer:
It's "bear in mind" meaning remember and take into account.
One of the meanings of bear is to carry, or hold up or support. So, you can carry something or hold it in your mind.
The only meanings of bare are in the context of lacking, including lacking clothes, decorations, or enhancements.
On the lighter side...
If you are imagining somebody naked, then it is bare in mind.
If you are imagining a big furry omnivore, then it would be bear in mind.