You should probably work through the fundamentals course in order to gain a basic understanding of how chords are commonly fretted & why.

https://www.guitartricks.com/course/fundamentals1

In general aim for the principle of efficiency of motion.  There are basic standards, such as use one finger per fret, index finger for lowest fret, going higher with additional fingers.  But sometimes concrete rules like that don't work because you need more than one finger in the same fret, notes are too close or too far apart for that rule depending on the musical context.

In this case, start with the basic open D chord fingering:  index finger on the A (2nd fret, G string), ring finger on the D (3rd fret, B string).  You don't need your middle finger in this voicing (normally on the F# 2nd fret high E string).

Hope that helps!