You need to be in Visual mode esc
then v
V
to select entire lined
(aka delete) to cut it, y
(aka yank) to copy itp
to paste (after cursor)P
to paste before cursore.g. you need to move between the NERDTree and Vim edit windows..
ctrl + ww
to toggle between windows
ctrl + w
then l
to go to left window
ctrl + w
then h
to go to right window