I am assuming you want to use natural evergreeens to make a wreath. You can use either a wire wreath form or a styrofoam wreath form. You can even bend a wire coathanger into a circle for use as a form. Stems of evergreen are wired to a metal wreath using florist wire, whereas with a styrofoam form the stem ends are pressed into the foam. The styrofoam is easier in one sense, but you have to be sure of where you want to place a stem as repeated poking weakens the styrofoam.
Gather your natural evergreen pieces. Be sure to place the cut ends in a bucket of water as soon as you take them so they can soak up water. Natural wreaths start drying up within a week. Here is a link showing one homemade wreath: https://www.wikihow.com/Make-an-Evergreen-Wreath
Here are a bunch of great options: https://www.countryliving.com/diy-crafts/how-to/g1056/diy-wreath-ideas/
I made one from Yarn ..Check it out https://justthatperfectpiece.com/braided-chunky-yarn-white-christmas-wreath-diy/
here are some great ideas https://www.hometalk.com/search/posts?filter=diy%20christmas%20wreath