The problem is that English has no palatal sound except /j/ (as in "yet" -> /jet/), while italian has "gli" and "gn" that use palatal articulation. Anyway, it is not so difficult to learn:
- position your tongue as if you were about to say /j/ as in "yet": the centre of your tongue will be close to the palate;
- now, without moving your tongue from there, push the middle of it against the palate as to let the air flow on the sides as you do when you utter "L": voice the consonant and the sound you are making is the proper "gli".
One more thing to remember: it is always double when in between vowels, so prolong it as you do for other double consonants in italian.
If you find it too hard to pronounce it properly, you can be still understandable if you say /llj/ as in "alien", but with double "L" sound: in practice if you say "follio" instead of "foglio", you'll be understandable. Anyway, try to get to a proper pronunciation of "gli".
I hope this helps^^