“Two steep and rocky steps, combined with a few flat sections through the meadows
— Steffen Hauschild
If you're taking the trail uphill, start at the end of Strada Varagna: a short and comfortable doubletrack for up- or downhill. Straight ahead, you'll see the top of Monte Altissimo.
Pass Monte Varagna to the south by taking a nice singletrack through the lower meadow. At the first steeper and rocky section, you may need to get off the bike. Then you'll reach the highest shoulder, where you can bike for some metres.
At the second steep section, the views down to Lago di Garda makes up for the effort. The Top of Monte Altissimo is hilly, so you can ride through the meadows to the cross at the highest point, passing the mountain hut "Rifugio Altissimo - Damiano Chiesa" near the top.
For the downhill, I recommend to take this trail also in uphill and inspect the harder sections. Maybe you're able to ride them all....