To practice the l sound, let your tongue touch the back of your upper front teeth.
Practice these words first:
Lake, late, less, least, lost
Call, melt, filth, cool, bold
Below, allow, rolling, balance, hello
To practice the tongue twister, read and say it slowly first several times, then you can say it faster as you get used to it. Always focus on the sound.
Little Kyle lay low while Lillian looked for Leila's lollipop that little Kyle lost.