How to add this on Tab

Hi,

Sorry to bother everyone, I am a self-taught musician and starting to learn how to Tab much of my work in Musescore, I found an old piece and wanted to transcribe, attached is the picture of the tab (Dm Chord), I was trying to find what is it called & ways to add it on the tab for days by searching the internet and reading the online handbook of Musescore, I am sure my way of searching fails because I don't know in music term what is it called, I just know how to play them when reading tab.

I figured out some of the bits & pieces by watching YT videos, reading the online handbook & forum.

Your kind assistance is highly appreciated.

Cheers,
Jeff