There are 2 ways to wear these:
1) For animation: equip the boots as normal clothing, then conventionally parent the trucks as custom Unity assets using a ParentHoldLink plugin, Macgruber's reworked version is easiest contained in his awesome Essentials collection. If needed, add collision using CheesyFX's excellent Heel Adjust plugin
To make the process faster for you, I've included a fitting-subscene in the var. Load your model in default pose at 0,0,0 then add a subscene and load from my var. The subscene is correct for the default model, you may need to adjust position and scale for yours.
2) For e.g. screenshots or scene visualization, it's easy to equip both the boots and trucks as clothing. Clothing plugins (ymmv) may conflict with Timeline, among other plugins, and I don't use them in animated scenes.
For anyone who doesn't know (I didn't until 3 months ago!): Character morphs which affect the feet may cause footwear to deform and this can be very noticeable with boots. Obvs if you've created your character this might be easy to fix, and I've updated my character Charlie with an optional shoe-fix morph.
Any problem with the skates, just give me a shout.
Check out more of my work here! https://hub.virtamate.com/resources/authors/cabaretnoir.90118/
The skates are a port of this model, heavily modified and repaired for VaM use:
"Neon Skater Skates" (https://skfb.ly/oMJJL) by tjgatt is licensed under Creative Commons Attribution (http://creativecommons.org/licenses/by/4.0/).