I have a 40 gallon tank and am trying to start an aquarium advice?

Hi, so I am 100% beginner i dont think I've ever actually owned a fish but I randomly find myself watching aquarium videos on youtube and am wanting to try getting into fish care. I currently have a 40 gallon tank that I was going seal the edges with silicone glue (I've seen people do this to make them leak proof?).

​

I'm not going to be making it right now i want to do all my research and buy my supplies first. But I was hoping for someone to help point me in a starting direction. I was thinking of doing a freshwater tank because I heard it is easier for beginners.

​

Any advice or suggestions would be greatly appreciated!