Hi!
To treat this you have to find the cause first. Usually conditions of heart, kidney, liver or low protein or severe anemia, which cause ankle and feet swelling, cause both ankles and feet to swell. Hence you will need to get heart function assessed by ECHO and EKG, get kidney and liver function tests done and get a complete blood picture for anemia. Low sodium in blood, hypothyroidism and malabsorption syndromes causing low protein in blood have to be looked into.
Since I cannot examine you and know other related conditions you may be having, nor is a detailed history possible on net, I have listed the various possibilities that should be looked into. Please consult your PCP for primary examination followed by proper referral.
Take care!