I made this teepee for my son's room after I realized how expensive it would be to buy off Etsy (eg over $100). I made this DIY teepee for around $30.

 First, use the tissue paper to make a pattern - 20 x 40 right angle triangle. Next, fold your curtains in half and pin down your pattern on the fold. Cut out 4 triangles.
 Here are the unfolded triangles and poles to judge placement.
 Use the leftover curtain fabric to make 4 strips (approx 10 x 40). Wrap each around the dowel and pin. Remove from dowel. Sew a seam along the pins (note, it does not need to be turned inside-out). In addition, you will want to sew a closure at the bottom of the strip (I learned this one afterwards).
 Next, take two triangles place their pattern sides together and lay a strip from above in between them (ensure the seam is on the outside). Sew all three together. Continue this around until all the pieces are sewn together. Cut one of the triangles to have a flap for the opening of the teepee.
He sanded the dowels and screwed holes into each of them approx 8" down the dowel.