How do I add pppd and other things into my buildroot image

I’ve been able to download and build the basic image using docker and the buildroot, but I need to add some customizations like adding pppd. I’m not very experinced with buildroot and with the scripts that do everything, I’m not sure where to go. I went into buildroot-2021.05 folder inside the buildroot folder and ran make menuconfig and I was able to pick out some packages that I wanted to include, then I ran the script again. The scripts seem to be using configs different that I ones I was editing with menuconfig. How do I go about building the image one step at time like kernel, rootfs, busybox and then roll it up into an image?

So I think I figured it out and I was pretty close. You need to run
make milkv-duo_musl_riscv64_defconfig
make menuconfig
now if I could just find the kernel configuration, I’d be happy.

That doesn’t work to build the rootfs, it fails looking for a different tool chain. I found the kernel config and I guess I could edit the defconfig and run the build_all command, but that doesn’t seem like a good way to do it and I don’t have a way to build a custom rootfs. I won’t be able to pppd as it’s not supported musl, but I’m trying to SLIP support for my project. I’m struggling with a lack of documentation (all things MilkV) and I’m not sure where to turn to get help. If anyone can point me in the right direction to get this figured out.