Resize canvas

Icon are often of the size 32x32 or 64x64. So, set a boundary on your workspace. Set the canvas size using Ctrl+Shift+D or File->Document Properties.... On the Page, you can define size your the canvas or resize the canvas to your drawing.

Resize object

In Inkscape, resize object is part of a transformation. To access Transform settings, go to Object->Transform...* or **Ctrl+Shift+M. Open the Scale tab and change accordingly.

Center icon to canvas

1. Select all your objects.
2. Open Object->Align and Distribute.
3. Select Relative to: Page.
4. Check Treat selection as group.
5. Click Center on vertical axis button.
6. Click Center on horizontal axis button.

Resize page to selection

Edit->Resize Page to Selection or Shift+Ctrl+R.