after installing DOSBox then drill down to
DOSBox folder on C drive and replace the orginal
DOSBoX 0.74 Options file with the one in this folder.

Local Disk (C:) > Program Files (x86) > DOSBox-0.74

The Following changes have been made to play in 
full screen.

fullscreen=true
fulldouble=false
fullresolution=0x0
windowresolution=0x0
output=overlay
autolock=true
sensitivity=100
waitonerror=true
priority=higher,normal
mapperfile=mapper-0.74.map
usescancodes=true