Start by tuning the first string (the one that the notes are played on) to the desired pitch. The ideal note is F4 but be careful not to break the string. The highest note you can achieve depends on the quality of the instrument and the strings.
What’s most important is not the highest pitch you can achieve but the relationship between the notes. The frets with dots on the handle represent whole notes while the other frets are flat notes. You may find that your instrument is slightly different depending on the shape, size and who made it. You can use a guitar tuner to achieve precise results. Using a tuner you will see that when the open string is tuned around F4 the other whole notes will align perfectly with the dots on the handle.
The second string (drone) is tuned 3 notes lower than the first string. For example if you tune the first string to F4, the second string should be tuned to C4. Hold down the second string on the third fret from the top and adjust the tension while strumming both strings. You will hear a beautiful tone when both strings produce the same note. Trust me you will know when they match!
Our great grandfathers did just fine without tuners so if you want to go old school and don’t care about the technicalities. Tighten the first string as much as possible without breaking it. Then adjust the second string while holding it down on the third fret from the top. Consider your cifteli tuned when you hear that golden sound!