Use a tuned guitar and a relaxed position. Stop if playing causes pain; reduce pressure and ask a teacher to check setup rather than pushing through.
For Em, place fingers on the second frets of strings 5 and 4; strum all six strings. For Am, place fingers on string 2 fret 1, string 4 fret 2, and string 3 fret 2; strum from string 5 downward. String 1 is the thinnest. Keep fingertips near the fret without touching it.
Pick each intended string separately. If a note buzzes, check finger placement and whether another finger touches the string. Correct one issue at a time.
Count 1โ2โ3โ4. Strum Em on 1, prepare the change, then strum Am on the next 1. Keep a slow steady count. Ten clean changes are more useful than fifty rushed ones.
Play two bars of Em, then two of Am, with one down-strum per beat. If the transition breaks the pulse, halve the pace. Finish with a version you can play comfortably twice in a row.
Begin by testing the same transition before adding a new chord. Progress when the notes ring clearly and the pulse survives the change.
Use the same comfortable counting pace for both sets. Count a change only if the intended strings ring and the next strum starts on time. Different speeds make this comparison misleading.