The 'radiator with integral expansion tank' has a small (~1cm diameter) threaded plug near the filler. If you are lucky, your Uno will have a similar plug in the pipes to the heater, on the bulkhead behind the carburettor.
Incidentally, make sure the heater is turned 'on' (red lever fully right).
Technique is to open the plug on the radiator (which is actually in the expansion tank), fill the radiator, remembering to reconnect the bottom hose first (your feet usually get wet at this point).
When coolant (you DID put green stuff in, didn't you?) comes out of the plug on the radiator, refit this plug. Leave the plug on the heater hoses off.
Continue filling the system until coolant comes out of the heater hose plug. Then refit this plug, top up, and start engine with expansion tank cap removed. You will have to wait for the engine to warm thoroughly (maybe go for a gentle drive) before topping up the level. Top up a final time with the engine cold.
Make sure that the heater works - if not, there may still be an airlock or the heater valve could be stuck. Because the heater hose is the highest point in the system, it is the last place to fill. If you don't have the threaded plug mentioned previously, you may like to disconnect the heater hose at the back of the engine bay and check that it is full to there.
Hope the job goes smoothly - it usually does for me. The only time I had trouble was with a stuck-closed heater valve.
BTW for anyone else, the Uno Turbo system is totally different and self-bleeding (I think it's a wonderful design, they put the expansion tank at the highest point in the system which is an excellent idea.)