Similar to an IRA, your share of the HSA must be moved by trustee-to-trustee transfer as a transfer incident to divorce. The funds are not permitted to be paid from your ex's HSA directly to you.
As rjs indicates, you must have your own HSA to receive the transfer. Easiest would be to establish your HSA at Optum, at least initially, otherwise the transfer would need to be coordinated between different HSA custodians. Once you have an HSA to receive the transfer, the transfer would be done under the instruction of your ex, the present accountholder, who needs to provide Optum with a copy of the divorce decree that stipulates the split. If your own HSA is at Optum, the transfer would be accomplished entirely within Optum. (If your ex is uncooperative, contact your attorney.) Establishing the HSA to receive the transfer and providing your ex with the account information is all that you need to do. Your ex must do the rest.
