Not my pic but same set up. How do I check the fuses that are in that white piece?

 

It's a visual inspection on that area. Any break in the fusible link means it blew out.

https://en.m.wikipedia.org/wiki/Fusible_link

 

Adding to the above....
If you've ever seen an open in the little ATC style fuses, it is the same visual inspection. i.e. if point A to point B is not connected it is bad and needs replacement. Look at the shape of the Z looking section. If some is missing its bad.

Alternatively you could remove the clear cover and use a test light (these draw a small amount of current, a good thing) and will light if fuse is good. A meter will work too.

Connect lamp to ground and probe the side farthest from the battery for all links. Once you begin your inspection it should make more sense. Of course if the main fuse is blown, it will not have power at all.
See attached.. btw main fuse is Good in this pic.