VFT can go without insects for a long time, probably forever, however: they will not be as robust and not produce many seeds. They can feed themselves readily. Insects will find the plant by it's nectar smell. I have two yearling VFT with traps barely 1/4 inch long. They are catching gnats and ants like crazy. If your plant is receiving plenty of light, full sun optimal, has plenty of distilled water, has acid soil with no fetilizer added, and is not dormant, then you can either wait and let it trap it's own prey, or if you just want to see it work, catch a mosquito, ant, or fly and feed it by hand. Make sure the insect is much smaller than the trap and alive. In my experience, moths contain too much body fat, roughly 50%, so the trap might rot (carnivorous plants cannot digest fat) if you feed large moths to it. In any case, do not overfeed your plant. Digesting prey takes a lot of energy for a plant, so it must be healthy before it can eat. Best bet, only "feed" your plant occasionally and leave it alone for weeks at a time.