If you intend to use FMLA, you must call the HR Service center. Their number can be found by searching FMLA on upsers.com.
They have a breakdown on there how FMLA works and also the eligibility requirements. In a nutshell though, if it is for you personally, any severe medical condition that does not allow you to perform your everyday job duties in a safe manor.
You must have been employed at UPS for the last 12 months and worked over 1250 hours in that 12 months. If not, you can still qualify for some leave under UPS' FMLA Policy. The HR rep will help you get pre approval pending your packet submission
They will email you a packet that your doctor must fill out and sign off on. Once that is done, you have only so many days to submit the packet, and UPS HR rep will make a final approval.
Once approved, when you call in, you must say you are using an FMLA day so your local management can record it correctly. Additionally, HR will give you an automated 800 number to call that and report your absence.
Additionally, if you are approved, the reason you are on FMLA is solely between you, your doctor, UPS' HR rep, and UPS' medical rep. Your local supervision team is not privy to that info, and beyond saying you are on FMLA, are not required to disclose the reason for it to them