English (Source)
Your Commander has already access to several towers. The first two are unique to your Commander and define their playstyle, many times being purely supportive. Build a few towers within range of the building, and make sure to build one which can actually attack.
Japanese Translation
司令官はすでに複数のタワーにアクセスできる。最初の2つは司令官固有で、プレイスタイルを決定し、多くの場合は純粋な支援用だ。建物の射程内にいくつかタワーを建て、実際に攻撃できるタワーを1つは必ず建てよう。