Linux commands not working

This is an incredibly basic question but I'm not super familiar with Linux; I only run it via my Steam Deck. So I went through the steps to install NextDNS via command-line client, it installed successfully, but then when I enter the commands it says to use, it says the commands are invalid.

I know I'm probably missing something super simple but Linux just makes no sense to me half the time. Can someone explain what I'm doing wrong?

Here's the relevant portion:

Congratulations! NextDNS is now installed.

To upgrade/uninstall, run this command again and select the appropriate option.

You can use the NextDNS command to control the daemon.
Here are a few important commands to know:

# Start, stop, restart the daemon:
nextdns start
nextdns stop
nextdns restart

# Configure the local host to point to NextDNS or not:
nextdns activate
nextdns deactivate

# Explore daemon logs:
nextdns log

# For more commands, use:
nextdns help

(deck@steamdeck ~)$ nextdns start
bash: nextdns: command not found
(127)(deck@steamdeck ~)$ nextdns activate
bash: nextdns: command not found
(127)(deck@steamdeck ~)$ nextdns log
bash: nextdns: command not found
(127)(deck@steamdeck ~)$ nextdns help
bash: nextdns: command not found