installing Docker

I love your tutorial, and I want it to work for me :) I’m using Kubuntu 20.10 on an old Mac. Here is how far I got today with the install:

trude@trude-MacBookPro:~$ sudo chmod +x /usr/local/bin/docker-compose
trude@trude-MacBookPro:~$ 
trude@trude-MacBookPro:~$ docker-compose --version
bash: /snap/bin/docker-compose: No such file or directory
trude@trude-MacBookPro:~$ 
trude@trude-MacBookPro:~$ docker-compose --version
bash: /snap/bin/docker-compose: No such file or directory
trude@trude-MacBookPro:~$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
trude@trude-MacBookPro:~$ export PATH="/usr/local/bin:$PATH"
trude@trude-MacBookPro:~$ docker-compose --version
docker-compose version 1.21.2, build a133471
trude@trude-MacBookPro:~$ docker-compose -f docker.dev.yml up
ERROR: .FileNotFoundError: [Errno 2] No such file or directory: './docker.dev.yml'
trude@trude-MacBookPro:~$ export PATH="/usr/local/bin:$PATH"
trude@trude-MacBookPro:~$ docker-compose -f docker.dev.yml up
ERROR: .FileNotFoundError: [Errno 2] No such file or directory: './docker.dev.yml'
trude@trude-MacBookPro:~$ 

How can I resolve this? Please :) Thank you