You can change a clip’s In point or Out point by dragging its edge in the Timeline panel. As you drag, the current In or Out point appears in the Program Monitor. A tool tip displays the number of frames that you are trimming: a negative value if you are dragging the edge toward the beginning of the sequence and a positive number if you are dragging toward the end of the sequence. You cannot trim past the original In and Out points of the source footage.
Click the selection tool
and
do one of the following:
To edit the In point, drag the left
edge of the clip once the Trim‑in icon
appears.
To edit the Out point, drag the right
edge of the clip once the Trim‑out icon
appears.

Trimming in this way affects only a single clip edge and doesn’t affect adjacent clips. To trim multiple edges at once or to shift adjacent clips, see Perform rolling and ripple edits and Perform slip and slide edits.
Press Ctrl
(Windows) or Command (Mac OS) as you drag using the Selection tool to
switch to the Ripple Edit tool.