I have the following regular expression for the set of all strings such that each block of five consecutive symbols contains exactly two 0's (consider the alphabet to be {0, 1}):
(0+1+ϵ)4+(11100+ϵ)r(0011100r)*(00111+ϵ)
r=11+(110+ϵ)s(0110s)*(011+ϵ)
s=(0+10)*(1+ϵ)
How should I convert this into an NFA? Please explain the steps behind it as well!
What you need is the Berry-Sethi algorithm, constructing the Glushkov's automaton.
However, for your problem, I'd consider constructing directly a DFA with $10 = \begin{pmatrix}5\\2\end{pmatrix}$ states corresponding to words of size 5 containing exactly two zeros, and a sink state (and maybe some other states for the begining of the reading).
The Glushkov's automaton on your regular expression will be very big.
