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
- Select all your objects.
- Open Object->Align and Distribute.
- Select Relative to: Page.
- Check Treat selection as group.
- Click Center on vertical axis button.
- Click Center on horizontal axis button.
Resize page to selection
Edit->Resize Page to Selection or Shift+Ctrl+R.