How to I install rust?

See https://www.rust-lang.org/tools/install
Or run:
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

How do I compile a rust program?

Use rustc
E.g. rustc main.rs
The output is a binary main.

Where does rust/cargo store dependencies

In you ~/.cargo/registry/ directory.

What is Cargo.toml?

It lists the details of your program/package and its dependencies.

What is Some in Rust?

Everything has a value in Rust (aka, a strongly typed language).

So Some may be used when assigning a variable to a value when may have a value of something, or nothing/None (no value).