Boolean algebra is defined as lattice which is isomorphic with $B_n$. I know how to construct Hasse diagram. But couldnt understand how to assign 0's and 1's to nodes. 
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Please tell the general mechanism for assigning boolean values to hasse diagram.
$B_n$ is defined as : If the Hasse diagram of the lattice corresponding to a set with $n$ elements is labeled by sequences of 0 and 1 of length $n$, then the resulting lattice is named $B_n$
In your diagram nodes can be seen at various levels. Level $k$ means exactly $k$ 1's are present in the length $n$ string.
A slanted line joining two nodes means a single zero in the node below has been changed to 1.
For example in the last diagram by starting with $000000$ for the bottom most element one scans the row above left to right and replace that 0 into 1. So level 1 it will be $10000, 01000,00100,00010,00001$. Continue in the same way until you reach the top which is a node with all 1's. Thats all.