Hi Tangmo,
Hope you are well
To make a silence at the start
1 Make a selection of empty space at the start even if its only a small selection
2 Go to insert on menu
3 Press "insert empty space at time selection"
4 If you do not have enough space because of lack of bars of empty space at the start just repeat the process again until you get the right amount of space you need.

To make space further into the project
1 Make a time selection of empty space where ever you have it at the start or end
2 Right click on the time selection
3 Press"Create Region from selection"
4 Drag regeion of empty space anywhere you want in the project .Im using a laptop so im pressing spacebar and the pad at the same time to drag not sure what it is on PC but its something simple

Its a tiny bit slow but works fine H