Nick89rs

Ok, so I've watched 10 tutorials and read a bunch on the wiki but I can't figure this out... I'm trying to test out reactors/engine combos in the VAB and I can't for the life of my find any fuel tanks/holders for the uranium floride the starter reactor uses and it has no fuel in it to start. Seriously what am I missing? Is this fuel only farmable and is there any way to test things out in sandbox without mining/refining?