To get started with the building process, you'll need to get familiar with Git and Repo.
repo init -u https://github.com/NAMELESS-AOSP-OPENSOURCE/manifest.git -b nameless
To save time, space and internet data during sync, use a command like this:
repo init -u https://github.com/NAMELESS-AOSP-OPENSOURCE/manifest.git -b nameless --depth=1
repo sync -c -j$(nproc --all) --force-sync --no-clone-bundle --no-tags
$ . build/envsetup.sh
$ lunch aosp_$device-userdebug
$ mka bacon -jX