The best way to mount bearings is to use a tool ensuring correct mounting forces, like a bearing press (see photo).

Generally the wheel hub diameter is not very stiff so that one believes he easily could mount the bearings by hand. It often works but this is not good practice Put the first bearing into the hub of the wheel and push it till the bottom of the hub hole. Be careful to press regularly on the outer ring of the bearing as to avoid any load through the balls during the mounting. See drawings.

Insert the spacer. Push the second bearing in the hub hole, in the same way as the first bearing.

After mounting we recommend to check by hand the rolling resistance of the wheel by hand. No noise and no vibration mean that the bearings are well mounted.

SKF STUNTmaster, SKF FUNglider, SKF SPEEDtrainer and SKF FREEstyler bearings must be mounted with the non-contacting seal on the outer side and metallic shield on the inner side of the wheel.
SKF SPEEDskater and SKF SPEEDracer mini bearings must be mounted with the seal on the outer side and the open side on the inner side of the wheel.

Removing instructions
Bearings must be removed carefully; otherwise there is a risk to destroy them or to make them more dirty than they were before.
Bearings should be removed in following cases:

Change or interchange wheels when worn.
Change when wheels are blocked or rolling badly.
Re-lubricate the bearings.
Clean the bearings.
Important observations:
Inline or skateboard or quads wheels are not designed for easy bearing removal. So, if you remove them without care there is risk to damage the bearing raceways. To do it properly SKF recommends to use a bearing press. See photo.

If you don't have it, the only way to remove the bearings is to use a handy tool with a hook at one end like the one shown

Here are examples of 2 cases for different axle diameters:

Axle of 6 mm diameter:

Push on the spacer
That will push out the opposite bearing.
Extract the spacer.
Hook the inner diameter and extract the second bearing
Axle of 8 mm diameter:

Hook the inner diameter of a bearing and extract it.
The spacer comes out easily.
Hook the inner diameter of the second bearing and extract it.