Initially, added clips appear in the top-left BINs (tabs for video/audio/images).. They can be trimmed there...
Drag the preview screen red-line cursor to the start point and SET START. Drag it to the end point and SET END. Then, on the sequence timeline, drag the cursor where you want the clip to be placed. Click the ADD button beneath the preview window and the clip appears at the cursor location.
You can also simply drag clips in full to the sequence and trim out the parts desired, using the SPLIT scissors that pops up when clicking the cursor or via the SPLIT button under the PV window. The chevron to the right of that button provides options to split specific tracks. After trimming, and deleting the unneeded portions, drag the clips right or left to join them.
To delete, select a clip and press the <del> key. Or right-click | DELETE. Or DELETE (ripple), which in most cases snaps all later clips to the left, eliminating the gap created by the deletion. GAPS can also be removed by a right-click on them and CLOSE GAP.
Transitions cannot be added to clips in the bin. That process is done on the main timeline, after clips have been arranged and butted together. The X in each clip brings up transition choices.
The FX icon in a clip is for effects, which also can be applied to the clips in the bin via a right-click | VIDEO/AUDIO EFFECTS. If that's done, the effects set there will be active when the clip is dropped onto the sequence. But this is not the case the other way around. If an effect is added to a clip on the sequence, it will not affect its source clip in the bin.
Check out the tutorials.