No apology needed!
On the clip page rows 2-7 correspond to the tracks 1-6 and the columns 1- 7 correspond to the selected clip (there are 16 key lit but only the first 7 can be selected). You can assign any track to any clip (clips can also be assigned to multiple tracks). By default the clips 1- 6 are assigned to tracks 1 - 6 (track 1 → clip 1, track 2 → clip 2 etc.). So you need to press the corresponding key to select a clip and load your sample there.
Yes, when a clip is loaded the start and end point are set to the start/end of the loaded file.