How do I erase on my iPad with my apple pencil (1st gen)?

If the app has an undo/redo function in it ( either spelled out or they use some sort of circular arrow symbols, one circular arrow going clockwise is redo, a circular arrow going counter-clockwwise is undo, something like that ) you use your Pencil to tap on these names, arrows, circular arrows. Every app is different how it displays its undo/redo feature.

OR

If the app has an actual eraser looking icon, you pick/tap on that icon and then use your Pencil draw ( erase ) over the mark you wish to erase to erase it!

An eraser feature may act more like a pencil/pen/brush stroke.

In some apps the eraser/draw/pencil/pen/brush tip size can be made larger or smaller.

There is NO eraser function/feature on a 1st gen Apple Pencil.

What app/s are you using the Apple Pencil with?

Use the eraser functions/features or the undo/redo features in the app/s.

Are you also new to iPad/iOS/iPadOS?