Converting your civil partnership depends on where the marriage took place.
If your civil partnership was formed inside of England or Wales
If you are in a civil partnership, you can convert it to a marriage if you registered in England or Wales. You do not have to convert your civil partnership with the same local authority that registered it.
You can also convert if you registered according to the law of England and Wales in a consulate or armed forces base overseas.
Changing your civil partnership to a marriage is called standard conversion. You can choose to simply convert, or you can follow the conversion with a marriage ceremony.
After the conversion you will receive a marriage certificate.
If your civil partnership was formed outside of England or Wales
If your civil partnership was formed outside of England or Wales, you can not convert your partnership into a marriage here, as you are in a legal relationship valid in the country where you formed it, although your partnership will still be recognized as a civil partnership in England and Wales.
This means you are not free to give notice of marriage. You should seek legal advice on the options available to you if you want to change this.