Cycling questions

Hello! Sorry if I've posted this in the wrong section or overlooked a relevant help thread/FAQ - I'm on my phone which doesn't help haha, & I'd like to make absolutely sure I'm doing everything right

I've had an empty tank filled with dechlorinated water for the past 3 weeks, with a low-level waterfall filter running, digital thermometer, fine rinsed sand substrate, some rinsed smooth river pebbles, a rinsed hide/decoration, and 5 low maintenance potted live plants. I now have a little of what I think is algae on the bottom and features of the tank (sorry, realise that makes me sound so amateur! I've never kept anything aquatic beside goldfish before) so for the purpose of establishing the tank, do I keep or remove it? I've also noticed a little black snail creeping about! Same question, keep or remove?

I've now bought a water test kit, (Nutrafin Test Mini Master) and live brine shrimp! Can I cycle with these? And if so, how? I've yet to do any water changes or a water reading as I'm confused!
Thank you in advance for any help! Trying to do the best I can for my future Axie

OK, basics first.
'Cycling' is the term for building up the good bacteria in a tank and filter. In order for this to happen you have to provide food for the bacteria in the form of ammonia. This is best done with no live stuff in the tank - you can add more ammonia if you don't have to support life. Ammonia is converted to nitrite, then nitrate by bacteria, then nitrates are removed with water changes. Live brineshrimp will not cycle the tank.

Remove the plants for now. Get some pure ammonia (less than £10 on ebay) and add enough to bring the ammonia levels to 4ppm. Test daily until all the ammonia is gone, add some more. Continue until 4ppm ammonia comes down to 0 ammonia, 0 nitrite and high nitrates in 24 hours. Change the water until nitrates are under 40ppm and you're ready to go. Add plants and axies!

This process is likely to take 3-4 weeks - you have to be patient.

Don't worry about the algae, it's normal in a new tank. It will be killed off by the ammonia as you cycle the tank.

sorry for my late reply - thank you very much Auntiejude!