"No Signal" is a message from your monitor that tells you it can't display the screen because the display mode the game has set (horizontal resolution/vertical resolution/color depth/refresh rate) is unknown to it. Even though it would be a good idea to implement old display modes in new monitors some companies have become lazy and dropped support for old display modes.

So you typically see the "No Signal" message because the resolution is either too high or too low (more likely in case of an old game) or the refresh rate is set to something else than 60, which is what most common monitors use today.

Two possible solutions exist:

1) Tell the game to use a different display mode. That can be tricky if you can't even see the menu. Some games allow to do that from outside of the game by editing a config file or passing the resolution as command line parameter. If it is a DOS game that is run via DOSBox you can edit the DOSBox config file to change the output resolution. DOSBox games from GOG even have a small utility to set the graphic options so you don't need to edit the config file by hand. Set the resolution to 1920x1080, then DOSBox will scale the game to that.

2) If the game has no method of changing the resolution outside of the game, the default resolution doesn't work and it isn't a DOSBox game you can also let your GPU do the scaling for you. I only know how to configure that on NVidia chipsets but other GPUs can do that, too. The options are probably named similar you just have to find them in your control panel. On NVidia it works like this:

*) Open the NVidia Control panel. Select "Adjust desktop size and Position".
*) On the "Scaling" tab select either "Aspect Ratio" (That guarantees that 4:3 display modes will not be distorted but they will have black bars on the sides.) or "Full-Screen" (Even 4:3 display modes will fill the whole screen but they will look overstretched.)
*) On "Perform scaling on:" select GPU.
*) Check "Override the scaling mode set by games and programs"
*) On Resolution and Refresh Rate select 1920x1080 and 60Hz.
*) Don't forget to click on the "Apply" button on the lower right.

See the picture. As I already said, AMD and Intel GPUs have similar options you just need to find them.

P.S.: That just makes the GPU scale up the low resolution graphic of the game so that your monitor can display it. Once you can see the in-game menu you still want to go into the graphics menu to set the game to a higher resolution to make it look better.

P.P.S.: Method 2 should work on any game. If you ever see "No Signal" again you can always try that.