You can use pos attribute (https://www.graphviz.org/doc/info/attrs.html#d:pos), e.g.:
xxx [
label = xxx
pos = "0,0!"
]
yyy [
label = yyy
pos = "10,10!"
]
You will also have to specify neato
or fdp
layout engine, so that dot
command-line would be (for fdp):
dot -Kfdp -n -Tpng -o sample.png sample.dot