Take a long 0,4 mm wire, and bend it.
Add a bead, and make a spiral with your fingers.
You add more bead, make a loop and add bead in the same way.
Now the branch is done.
You make more branches.
After you have couple of branches now get them together. Wrap some wire on them.
Now the branches is done!
You can make another branches in the same way and assemble them together.
The tree is done. Use your imagination after...;)))
There are many other tehniques... Use the one you think is much easier for you.
Please give credit to Beatricedesign