AHey guys! So I have read quite a few threads about how to crumb coat a cake but it doesn't really give me detail for detail on how to do it! When I apply the fondant, I want my cake to look super smooth , because some of my cakes in the past have came out some what bumpy and I always hated it! Can anyone help me out with this! I would really appreciate it!!! Thank you!

There are plenty of tutorials, both here and on youtube, that will show you how to get the super smooth finish to your cakes.

But regarding your question about crumb coating: What you do is apply a thin layer of frosting all over your cake first - this is just to trap the crumbs so they don't interfere with your next layer or your fondant. Refridgerate your cake for a while, then go back and apply more icing - this is the layer where you have to take care to get your edges straight etc. No need to be super careful about your crumb coat, just make sure you cover your entire cake - and of course it's preferable to make it as good and straight a "base coat" for your next layer of icing as possible. But don't use a whole lot of icing for your crumb coat - just enough to tie up those crumbs and fill in any gaps in the cake / between the layers. Good luck!
 

AThank you very much. One more question. After I refrigerate the cake and apply the second coat of icing, I can cover it with fondant right away? Or does it have to go back in the fridge?

AOn this video she has a very thin crumb coat on her cake she than refrigerated her cake for a few minutes than does another layer of buttercream getting that layer extra smooth and nice so that when she places the fondant on the cake it looks nice.

m.youtube.com/#/watch?v=6Vgcx5GZTnM&desktop_uri=%2Fwatch%3Fv%3D6Vgcx5GZTnM

She than places the cake in the refrigerator gets it cold than places the fondant on

m.youtube.com/?reload=3&rdm=mm6rke7kd#/watch?feature=fvwrel&v=wYeMTCajw8E

I don't know who started the idea of friging a cake to 'set' the crumb coat but that was *never!* done before.

A crumb coat is a super thin coating of b'cream icing that is allowed to dry at room temp.  This should take only a few minutes (not much more than 15 minutes at most) depending on the icing recipe being used. 

IF the recipe is a non-crusting one, then yes, friging is probably needed.  The thin coating of b'cream should look much like a glazed donut. 

It is intended to seal in not only crumbs but moisture so the cake will remain moist while being worked on.

Once you can lightly touch the crumbcoat w/your finger and nothing comes off it is ready to be finished iced.

And once the finished icing coat is done you are ready for the fondant.  In fact, the b'cream needs to be fresh for the fondant to adhere to it - not refriged nor allowed to dry/set up.