Hey Chandra,
I assume that you use vmd for visualization. Try using the command "pbc wrap" (without the quotation marks) in the vmd console. Espresso stores the un-wrapped coordinates in the vtf file and this command tells vmd to fold them into the box.
Of course, check that pbc are activated in you system
Alternatively, you can change the behaviour of writevcf() in the file
src/python/espressomd/io/writer/vtf.py
to print part.pos_folded instead of part.pos. This makes espresso print the folded coordinates directly into the vtf file.
Best,
Martin