How can I best prepare for this program?

Generally, it’s best to have a semester or two of college-level Japanese language learning under your belt.

On your own, the most effective thing you can do is to memorize your hiragana and katakana (about 100 characters), including writing it in the correct stroke order. These are taught in the first week of Level 1, and students are tested on it after that first week. This way you can get a jump on what would otherwise be a difficult challenge.

In addition, in each level of instruction, students are expected to learn about 150 kanji, each term.

This KCP blog post contains several great resources to learn Japanese characters:

Learn Japanese Online.