Fun fact: ALE doesn't check your code. ALE doesn't produce any warnings.  
What ALE does do, it *runs code checkers* that do the actual code checking and aggregates their output.

The question doesn't say but it's pretty obvious this one's about Python.

The first (and almost only) ALE command you need to know is `:ALEInfo`. It will show which tools were run and the warnings they reported. It's a lot of text and you will need to scroll down for a bit.

In my example, I see
 
    C0103 (invalid-name) Variable name "camelCase" doesn't conform to snake_case naming style

reported by `pylint`.

You can Google how to shut `pylint` up.  
I'll show two ways. You can set a variable for ALE to forward to `pylint`

    :let g:ale_python_pylint_options='--disable=C0103'

which will work within Vim for all your Python code.

The alternative is to create a simple `pylintrc` like this one

```ini
[SECTION MANDATORY BUT IGNORED]

disable=C0103
```
This can be per-project or globally and will prevent the warning independently from Vim.

Either way, the warning is gone.

I'd like to emphasize that [PEP-8 wants snake_case](https://peps.python.org/pep-0008/#function-and-variable-names) so it's better to use snake_case identifiers instead of disabling the warning. If it was my repo, I'd bluntly reject such code.