Help needed - refilling radiators

[nunu73]

Morning all, we've just moved house and I've replaced some of the rads in the bathrooms with towel rails... I can't for the life of me work out how to refill the system though from the boiler...

Any help in terms of where the filling loop is on the picture are gratefully received

 

[muggles]

 

[nunu73]

Oh god, really that simple??? Thank you @muggles ...

Next question then... which pressure gauge do I need to keep an eye on? I'm assuming a third of the way up on the left

 

[muggles]

Yep that's the one