You can create slow motion two ways.

One way is to grab unto the right end of a clip then while holding down your left mouse and the Ctrl key drag right. You'll see a ziz zag line indicating the section is stretched. First spint into just the area you wish to have slow motion. Assuming you want 20 seconds of the time line to be slow more isolate that section splitting prior to draging. This adds frames and thus time So if you event was 20 seconds and you stretch it, you'll end up with 22, 25, whatever seconds depending on how far you stretched. Unlink any attached audio track first.

The second method involves using a envelope. Click in the event you wish to effect. From the Menu Bar Insert, Video Envelopes, Event Velocity. You'll see a green line in the event you clicked from Doulble click anywhere along the line to add a node (little square) add as many as you need to effect velocity. Holding down your mouse drag the node up or down and a readout will show the relative velocity. This method does not add frames. You'll still get slow motion by the time factor isn't altered.