Single-wire FM antennas are admittedly limited in performance. Like all antennas, height and distance from obstructions are key, and in general, outdoor antennas perform a lot better than those inside a building. For internal use, a little experimentation can determine the best configuration for a single-wire antenna.
Disconnect the antenna, if it's already attached to the radio, by pulling oot the antenna plug from the jack usually found on the back of the tuner. Alternately, it might be necessary to loosen a screw or screws that serve as the antenna terminals on the tuner to release the wire. Untangle the antenna, stretching it out its full length to maximize its reception surface area.
Reconnect the antenna after untangling. Turn on the radio, tune in your favorite station and raise the end of the antenna as high as possible, moving it in small increments from side to side to determine the best placement. If the environment is conducive to it (and the antenna is long enough), move about the space with the antenna in hand and note the changes in reception. If possible, access an attic or rooftop to get the most height. Continue this process until the best reception is achieved.
Tape the end of the antenna in position temporarily. You may notice a drop in signal strength when you are no longer touching the wire, which is normal, and you may have to readjust the antenna's placement until you get acceptable hands-free signal strength. Then, walk around the room where the radio is to see if your movements interfere with the signal at any point--this may require further adjustment. When you find the configuration for the best results, mount the antenna more securely, perhaps wrapping the end around a nail or a screw in the wall.