When choosing which distribution certificate option to use, you have three options. This is what they mean and when you should choose them:

1. Use distribution certificate details from your latest submissions 

Use the same certificate that you choose for the last submission. This option will only be visible if you have done one or more submissions on your organization.

2. Generate a new distribution certificate

If you have no distribution certificates, or if you want to use a different one, you can generate a new certificate. Keep in mind that an apple developer account can only have a maximum of 3 distribution certificates and enterprise accounts have a maximum of 2.

3. Upload your own distribution certificate (.p12 file)

You can upload a different distribution certificate to use for this app submission. Use this option if you already have a .p12 file and don’t need to generate a new one. If you have reached the maximum number of distribution certificates that your account can have you have to upload one for Fliplet to use. 

The p12 file isn’t stored under your Apple Developer account, so you can’t download it again from here. Most likely your IT team will have the files available on their systems.