You can move the currently active Vim split by pressing ctrl-w followed by a capitalized movement key: H, J, K, or L:
ctrl-w H moves the active split to a full-height split across the left
ctrl-w J moves the active split to a full-width split across the bottom
ctrl-w K moves the active split to a full-width split across the top
ctrl-w L moves the active split to a full-height split across the right