The tenor recorder has a mellow sound many people find appealing. Weighing in at about a pound and measuring two feet long, the tenor is bigger than the soprano or alto. It is not a good choice for a child because the distance between the holes will be too wide for small hands. The fingering is the same as the smaller recorders, though, so the transition from one of the them to the tenor will be easy.
Remove the caps from the long, middle section of the recorder. Fit the top and bottom sections onto its ends. The hole in the top section should align with the holes in the middle. The lever on the bottom section should be slightly to the right of the hole above it.
Hold the recorder with your left hand on top, left thumb over the hole in the back, and left fingers covering the top three holes. The little finger can rest against the body of the recorder--it doesn't cover a hole.
Rest your right thumb under the stop on the back of the instrument, if there is one. Your right fingers should cover the remaining holes naturally. Your little finger will use the lever at the bottom. You may need to twist that section to get a good fit.
Close your lips over the top of the mouthpiece. With the tip of your tongue in place to form the letter "D," blow into the recorder and allow the tip of your tongue to drop.
Use the fingering chart that came with your recorder or the one at the link below to play a scale. Release the lever to form the first interval.
Get comfortable with the scale. Then think of a simple melody and see if you can play it. Because the recorder is a fairly straightforward instrument to play, you can improve rapidly by practicing on your own.
If the recorder feels heavy, attach the neck strap to the recorder and slip the loop over your head.