We have a Optima XL and were told we needed a new Battery which we now have,all the red lights are on but we fitted the new battery bur no green light comes what do we need to do?

Who told you it needed a battery?

Has a fuse blown?

Does the charging circuit actually work?

Have you put the lid on and reset it?

Agreed who told you that?

Also have you entered the code when powering it up? 

Sounds like you may have been too late with the battery replacement, down power power up mains first then battery, but be warned that may get the panel back up and working (if you are lucky) it doesnt mean that the panel is okay. If the battery has been dead for a while then its likely to have done irreparable damage to the charging circuit