install build dependencies
sudo apt install cmake libsdl2-dev libsdl2-image-dev libsdl2-mixer-dev libsdl2-ttf-dev libsdl2-net-dev libvorbis-dev libboost-all-dev libpango1.0-dev
clone repo
git clone https://github.com/wesnoth/wesnoth.git
first build
mkdir wesnoth/build && cd wesnoth/build
cmake ..
make
launch program
./wesnoth
make changes to code (or do a git pull), then in the build folder created earlier run make again
make