I have had slight swelling in my left arm due to lymphedema. What can I do?

Lymphedema therapy. Manual lymphatic drainage and complete decongestive therapy are the cornerstones of proper lymphedema care. You should seek the opinion of a vascular specialist that has a special interest in lymphedema management. You can learn a lot of the techniques and can begin self management at home once you have been properly treated.
Compression. Lymphedema can be frustrating as it requires constant attention, especially if severe. With regular use of compression sleeves and massage it should be controlled resonably well.
Compression , enzyme. Compression garment can reduce lymphedema and oral enzymes such as bromelain, serrapetase can be helpful of the area is not sclerotic.