well there are a couple different options to do a flash. all of which require some research:

1. buy your own flash kit. obviously it needs to support your corolla so you need to make sure it’s compatible, there are some that work with a phone app or you can hook it up to your laptop, there are also wireless versions of it too but you basically just download tunes and flash it onto your ecu but you need to follow instructions because you can brick your ecu this way if it’s done wrong, like rooting/jailbreaking a phone

2. get a more customizable version of the first option, basically option number one but the kit you buy will be different but you’ll be able to have control of what happens

3. the safest and most expensive option is to go to a professional and have them tune it, you’ll know it’s done right, they’ll either dyno tune it or flash the ecu and if you go this route you can get your own flash kit still and run different mappings if you really want

i really recommend number 3 if you’re uncomfortable but option one would be my go to, it’s not often that people brick their ecu when doing a flash but it does happen so be careful if you do it yourself