The 2.4 kernel comes with LVM already included although you should check at the Sistina web site for updates, (eg. v2.4.9 kernels and earlier must have the latest LVM patch applied ). When configuring your kernel look for LVM under Multi-device support (RAID and LVM). LVM can be compiled into the kernel or as a module. Build your kernel and modules and install then in the usual way. If you chose to build LVM as a module it will be called lvm-mod.o
If you want to use snapshots with ReiserFS, make sure you apply the linux-2.4.x-VFS-lock patch (there are copies of this in the LVM/1.0.6/PATCHES directory.)