First, get dwm.
$ git clone https://git.suckless.org/dwm.git
side note: you also need dmenu (required), and probably st (you can change it).
dmenu is a launch menu, and st is an annoying terminal app, but i use kitty instead
$ git clone https://git.suckless.org/dmenu.git
$ git clone https://git.suckless.org/st.git
Now, configure them each and compile them. The steps are probably the same for each repo.
$ cd dwm
$ cp config.def.h config.h
$ nvim config.h
Edit the config to your liking (it's just C code), then compile and install.
$ make -j4 && sudo make install
This can be done for all three of the projects.
Now, to start dwm, I don't know how to make configurations for sddm, so here's the dumb way that I use:
$ nvim ~/.xinitrc
exec dwm
After that's done, go into a tty, and run the following:
$ sudo systemctl stop sddm
$ sudo systemctl disable sddm
$ startx
This will hopefully run your .xinitrc file and start dwm.