Glue the concave mirror just inside one end of the larger cardboard tube with the curved side facing into the tube. Allow the mirror to dry in place completely.
Thread fishing line into the large needle, and run it into the tube a few inches from the end opposite the concave mirror. Knot the fishing line where it entered the tube, and leave the end inside the tube threaded into in the needle.
Measure a 45-degree angle within the tube from the fishing line's entry point, using the protractor. Mark where it would end on the side opposite where the fishing line entered. Run the fishing line through this point so that it makes a 45 degree angle through the tube. Repeat this with two more lengths of fishing line on both sides of the initial one.
Glue the smaller mirror to the three angled fishing lines so that the reflective surface faces the concave mirror. Allow the smaller mirror to dry in place completely.
Puncture the large cardboard tube directly above the reflective surface of the 45-degree angle with the utility knife. Check to make sure you can see a reflection of the end of the tube, and cut around the puncture to make a hole with the same diameter as the smaller cardboard tube.
Cut a 2-inch length of the smaller cardboard tube, and insert it into the hole of the same size in the larger tube. Glue it in place, and allow it to dry completely.
Glue the eyepiece lens into the outermost end of the smaller tube. Once everything is dry, you should be able to point the telescope out a window (concave mirror end farthest from the window), and see images through the eyepiece lens.