Simply create a textarea matching your design in size and location and mark it by special amy attribute. Then load Amy using <script ... tag with desired bundle and theme. All bundle snippets will be working, as well as key shortcuts (such as Esc for word-completion, (Shift+CTRL+)F2 for bookmarking and so on). Read the source of this page for the exact way of embedding. It's unfashionably simple ;).
Amy Editor website | Amy Editor Manual.