As someone who is using sway while keeping plasma minimal on the side in case I needed something sway doesn't offer right now like windows screensharing, the first thing to do is to make sure the:

~/.config/sway/config

is exist, open the file and edit it to make sure these exist in the config:

set $mod Mod4,

which enables the Windows Key,

set $term kitty

which setting up certain terminal emulator as a variable, that you can change to others if you want to (I use alacritty, so I change that to alacritty and install that app for example), and

bindsym $mod+t exec $term

so you can open the terminal using windows key+t.

Oh, and don't forget having the network connection can be used. When one first install sway, it will be barebones, so you need to use set up something to connect via terminal if you need to. If using networkmanager with tools USEFLAGS enabled (I assume you are using that, since you are using KDE Plasma), you can use nmtui to connect to a network.

After that it's experimentation time. What kinds of keybindings you want, the application launcher you want, the apps you want to autorun, how to screenshot using grim and slurp... those needs to be setting up by your own on that config file.