Sometimes buyers will accept alternate submissions from the same proponent while others will not. You will know if you can submit multiple submissions if the following message appears on your submission confirmation page:
You can also tell from reading the Submission Instructions included in the project via the "Unique Per Alternate" descriptor. The Submission Instructions will also outline which pieces of Requested Information require a new file upload for every alternate submission, as well as the maximum number of alternate submissions allowed.
If you don't see either of these messages then that means the bid administrator hasn't enabled the additional submission feature. If possible you can try reaching out to them and ask them if they'll consider turning it on for you or accepting another response another way.
If an organization you are submitting to is accepting multiple submissions you will be able to submit a Primary Proposal along with Alternate Submission(s). You can prepare both at the same time), however a Primary Proposal MUST be submitted and finalized before you can submit an Alternate Submission, otherwise you'll receive the following message:
You can choose which proposal to work on under the Submission section of the listing page.
Do note that when preparing an additional submission, you will only have to re-submit files for the Requested Information slots tagged "Unique Per Alternate", as the other files are considered common (i.e., only need to be submitted once) and you are requested to upload them with your first submission:
If you begin an Alternate Submission, Bonfire will make it very clear with Special Instructions indicating that you may only upload for the Unique per Alternate slots.