Some pretty important things: Make sure the tank is rather humid (you can just use a spray bottle with water, but make sure it's dechlorinated, as water treatment chemicals can be especially harmful to invertebrates, fish, reptiles, and amphibians-there's also misting machines specifically built for vivariums like yours)-but the tank NEEDS to be properly ventilated, otherwise mold will grow in the tank, and if you're living with your parents or a roommate, they probably will not like that, and your tank will look like you were trying to make a diorama based on The Last Of Us-which I would assume is not your goal. I'd recommend using some kind of wire mesh lid, but if you could send me the tank that you got-preferably the page you got it on if you got it online-that would be appreciated so I can find out all the technicalities of your enclosure and what you can do with it. Young praying mantis really like fruit flies and gnats, while as adults, they really like crickets, and no matter what age they are, they'll only eat live food. Depending on what type of mantis you have, I'd also say you should decorate the enclosure accordingly to their habitat. Try and make a bioactive enclosure if you can-essentially, go for live plants, and have a bunch of other creatures in the enclosure (if they all live in the wild habitat of your mantis species, of course, and they also can't predate on the mantis-so having a gecko to represent Godzilla is a no-go.) A bioactive enclosure requires a lot less care (though you still have to pay attention to it, and care for it accordingly)-the mantis has a ton of free food sources, but pay attention to what actually gets in the tank-some hitchhikers can kill a mantis. There's a Kamacuras swarm worth of YouTube videos of bioactive enclosure ideas for various life stages, species, and enclosures, so watch those for some ideas. It's extremely important to NEVER, EVER, EVER overfeed the enclosure. Essentially, the mantis could be eaten alive by whatever you're feeding it. The bioactive enclosure usually has enough food for the mantis, so you shouldn't need to add too much more unless the mantis isn't eating. I wouldn't say imgflip is the greatest place to ask for vivarium advice-go watch a few YouTube tutorials instead.
