To build a kernel, the package kernel-source must be installed. Additional packages, like the C compiler (package gcc), the GNU binutils (package binutils), and the include files for the C compiler (package glibc-devel), are selected for installation automatically by YaST.
After installation, the kernel sources are located in /usr/src/linux-<kernel-version>. If you plan to experiment with different kernels, unpack them in different subdirectories and create a symbolic link to the current kernel source. Because there are software packages that rely on the sources being in /usr/src/linux, maintain this directory as a symbolic link to your current kernel source. YaST does this automatically.