There are basically two ways to insure your handbag.
Specialist cover
There are specialist insurers that will provide cover specifically for your handbag. They primarily cover it against damage or theft, but some also provide cover for the contents up to an agreed limit. This is typically up to £1000, but it can vary depending on your policy provider.
If your handbag is particularly expensive, you can purchase policies from specialist designer handbag insurers. This kind of policy is only offered by a few insurers, and it will have a much higher limit on how much you can claim in the event of damage or theft. Naturally though, this kind of cover will be more expensive.
Home contents insurance with personal possessions cover
As an alternative to standalone handbag insurance, your handbag may be covered on your home insurance personal possessions cover. Whether either of these apply to you depend on your circumstances, and whether you need your handbag covered in the home, or when out and about.
If it's not covered as standard, you can add high value items to your cover individually. Usually this applies to items worth £1,000 or more.