I have looked at other similar questions on this site but couldn't answer my question. I have a model made of cubes the edges look very sharp (I would put a picture here but I don't have the required rep) is there a simple way to make the edges round?
You could use the Bevel Modifier from the properties panel.
Example with Segments set to 3 and Width 0.1 (red cube) Width 0.3 (blue cube)
stacker's answer answers the question. However, you can also selectively bevel parts of your mesh with Ctrl + B which is often faster than using the modifier if you want to bevel certain parts of your mesh (the modifier has options where you can bevel a group of vertices etc). You can also bevel single vertices with CtrlShift + B.
Also see Most efficient way to round edges and How can I make sharp geometric 3d models look more realistic? for more tips.
You can also decide to do it the manual way. Add loop cuts Ctrl + R close to the edges of the cube in all directions (or as needed).
Then apply a subdivision surface modifier Ctrl + 1 - 6