い adjective
あかるい
このへやは明るい。
This room is bright.
トーフグの社いんは、みんな明るい。
Tofugu workers are all happy people.
未来はまだまだ明るいよ、おじいちゃん。
Your future is still bright, Grandpa.
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of bright? It's also bright.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
You have to remember the あか portion. What is あか in Japanese? It is "red." So, think of something that's really bright. Now, imagine it being totally red (aka あか). In Japan, the color red is associated with the sun, and the sun is pretty bright. If you can remember this you can also remember the reading of this word.