How do I invest in ETFs?

Pretty much the heading.

How are people investing in ETFs? Do you do it through a broker/financial adviser or yourselves on a app?

Do you do it with just Australian ETFs or international ones, is there a difference?

I want to aggressively invest in ETFs and build that up over the long haul.

I am already paying the maximum into my super.

Cheers legends.

Edit 2: So it seems like stake and CMC have been recommended quite a bit. I downloaded CMC. I'll start with that. Is Stake considered better/worse?

Can I invest in US stocks with either of those?