Place the top of your tongue on your palate, take air and then pronounce the R with a lot of force, it's almost like a vibrating sound. It might help you if you think of it as the sound of a motorcycle engine and try to replicate it

you know what? I'm native spanish speaker and I have a condition called "frenillo" in my mouth that dont allow me to pronounce correctly the "rr" sound...take note that even for some people who speak spanish is tricky.

I learned a technique as an English speaker learning Spanish that works pretty well. If you say the word ‘Butter’ with an American accent, that ‘tt’ sound in the middle actually mimics very well the Spanish ‘r’ sound. If you say ‘Butter’ quickly and in rapid succession, you can accidentally start trilling that ‘tt’ to mimic the ‘rr’ sound in Spanish. When that happens, just try to sustain it until you can produce the sound on your own. Hopefully that made sense and let me know if you need further clarification.

In order to pronounce the r sound in Spanish, you have to place your tongue in a different position than when you pronounce the r in English.

Muchas gracias, de nada!