Your landlord may have originally offered you a deferment for a period which may now be ending. Each landlord may have different requirements for collection on the deferred amounts. Some may want all of the missed months at once while others pay allow you to set up a partial payment in addition to your regular rent.
Your first step anytime you are experiencing an issue paying the rent should be to contact your landlord and explain to them the situation as soon as possible. By being proactive it can show your landlord that you are trying to be as responsible as possible.
Propose to the landlord a payment arrangement that may work for you both, however the landlord is not required to accept any partial payment agreements. If your issue is temporary your landlord may agree to a proposal in order to keep you as a tenant especially if you have been current for most of your residency.
If your issue will be on going or if your landlord does not agree to make any adjustments, you will want to look at other options for help. Agencies like the Housing Authority or Department of Human Services (DHS) may be able to provide temporary assistance with making rent payments. Friends and family may also be able to assist you temporarily in order to get everything back on track.