This is a drawing of the alveolar ridge: https://upload.wikimedia.org/wikipedia/commons/thumb/7/75/Places_of_articulation.svg/1200px-Places_of_articulation.svg.png
As a native speaker, I make the rl sound in parlo with the tip of the tongue between position 4 and 5, where you can feel your palate is starting to curve upwards. It's basically the point between the first two (the one closest to the teeth) palatal rugae (those hard ridges on both sides of the hard palate).
Start raising and placing the tip of your tongue between them, very very lightly, then try to let the air flow above the tip, between the tip and palate. You may want to start with the unvoiced sound of R, as it should be easier. The tip must be relaxed and free to "flap", otherwise you will get the L sound (coming to that later), so make sure the air is not flowing from the sides of your tongue. Keep blowing more air and at some point the tip will start to roll and if you've ever seen Jurassic Park, the sound will vaguely resemble the one of a Velociraptor...
From here, try to go for the voiced consonant. You won't need to blow as much air for this one, but the little air will still need to flow from the tip of the tongue brushing against the alveolar ridge.
For the L sound, the tip of the tongue is in the very same position, but it touches the palate and lets the air flow between the sides of the tongue. The sides of the tongue both touch the row of the upper teeth.
Now, with the rl cluster, it's a matter of going from a relaxed to a "tensed" tip of the tongue. Pronounce the R, let the air flow in one direction, then cut that flow by touching the palate (and stopping the tip from rolling) and the air will automatically flow through the sides, creating the L sound.
I hope this helps. The rolled R sound can be difficult for natives too, and some of us never learn it and resolve to using the French R sound instead.