Its not always necessary but makes it easier. Once the tyre is on you can inflate to the recommended PSI, you can use some Schwalbe Easy Fit to help the tyre slip into place under the rim bead.If you do need to use tyre levers be careful not to damage the new tube. Now you can put the other side of the tyre on the rim, if possible do this with your thumbs as levering a tyre on can sometimes pinch the inner tube.Insert the inner tube into the tyre with the valve in line with the valve hole in the rim.

Inflate your new inner tube just enough to shape it (a couple of pumps), this will make it much easier to fit - Don't try to fit a fully deflated 'floppy' inner tube as you will probably nip it when fitting.

Once happy, put one side of the tyre back on the rim.

Check the tyre (if not replacing) for any sharp objects, do this by running your fingers around the inside carefully and remove foreign objects.

Check the wheel for any sharp objects / rough surfaces that could cause a puncture.

Remove the inner tube, and then you can take the tyre off completely.

Use a tyre lever, or two levers if your tyre is tight, and lever one side of the tyre off the rim.

Deflate the inner tube, once the air is out, pinch the tyre walls together to make it easier to lever off.

Remove your wheel from the pram, (not always necessary but makes life easier).

If you are just fitting a new inner tube:

Guide to Fitting Pram Tyres and Inner Tubes

Mamas and papas skate pram instructions