The sea-of-gates router is able to take an arbitrary set of unrouted arcs and convert them to layout.
To do this, use the Sea-Of-Gates Route command (in menu Tools / Routing). If there are unrouted arcs selected, these will be the only ones converted. Otherwise, all unrouted arcs in the cell will be converted.
The Sea-of-Gates router uses metal layers in the current technology. You can disable the use of any layer, or favor it above others to guide the routing. To do this, use the Routing Preferences (in menu File / Preferences..., "Tools" section, "Routing" tab).
Another control found in the Routing Preferences sets the maximum width of a route segment. By default, each segment is made as wide as the widest arc already connected to that segment. However, in some situations, very wide arcs exist, and the connecting routes should not be that wide. By setting the maximum width, this limits the size of generated layout.
Yet another control in the Routing Preferences sets the maximum number of steps that the router will take to find a route. The larger the value, the longer the router will run until giving up.
The final Routing Preferences control the use of multiple processors when doing a Sea-Of-Gates route. If your computer has only one processor, these controls are ignored. The "Use two processors per route" preference is the best use of two processors because it uses two processors for each segment that is to be routed. The "Do multiple routes in parallel" preference attempts to use as many processors as possible to run multiple routes at once. If your computer has two processors, it is recommended that you use "Use two processors per route" to get the best performance. If your computer has four processors, it is recommended that you check both options so that two different segments can be routed at once and each can have two processors working on it (as opposed to checking only the second preference and having four different segments routed more slowly but in parallel).