See the attached screenshot. In the FFF Settings window, show the "Advanced" stuff, then go to the "Other" tab. There are the speed settings. The "Default Printing Speed" is the X/Y motion speed when extruding (unless you override, like on the first layer, outermost perimeters --- right below it as a percentage of that speed --- etc.). The "X/Y Axis Movement Speed" is the speed for non-extruding rapids. This is the one you want to reduce.
Don't be afraid to dink with the Advanced stuff. Look around -- there are a lot of things you can work with on temperatures for layers, infill settings, etc., etc., to help improve your prints. Read through other posts here and see what folks have found useful. One word of advice: don't mess with ten things at once! Change one or two and see how your prints change and make incremental improvements. You'll find what works for you by experimenting and learning. I understand that S3D is working on a manual that will have more info on what all the settings do in some detail. (You can pause the mouse over a setting to get a brief tooltip.) Can't wait to read it!!!
- FFF Settings, Advanced settings showing, Other tab, showing printer speeds