@diefledermaus you always start with statutory leave and pay.
Essentially you have 52 weeks Statutory Maternity Leave (SML) leave. You must take the first 2 weeks after birth as SML (plus any weeks you chose to have before you give birth). This leaves a maximum of 50 weeks to share.
Your DH will get 2 weeks Statutory Paternity Leave (SPL) which he must take within 56 days of you giving birth. This is often taken at the same time as the 2 weeks SML.
Decide if you want to take leave at the same time, in blocks and or to cover the whole 12 months. Use the ACAS template to write it down - this helps you work out the leave and pay https://www.acas.org.uk/sites/default/files/inline-files/Shared-parental-leave-forms-for-maternity.docx
https://www.gov.uk/shared-parental-leave-and-pay/applying-for-leave-and-pay
https://www.acas.org.uk/shared-parental-leave-form-templates
You have to actively opt out of SPL so you can both get Statutory Shared Parental Leave (ShSPL). There are pros and cons but one potential benefit of ShSPL is that you both get 20 SPLIT days plus you get 10 KIT days. Note: your employers have to agree but using these strategically during the unpaid part of SPL/ShSPL can be helpful in giving you additional income.
Now we get to pay, you get 39 weeks in total but SMP gives you 90% of salary for the first 6 weeks. So it makes sense to have SML and SMP for the first 6 weeks. After that you get 33 weeks of either SMP or ShSPP. You have to align SMP or ShSPP to the weeks of SPL and ShSPL. Using the ACAS template really helps.
If you are eligible for occupational pay this is usually a top up to SMP and ShSPP so must be taken at the same time. Your respective employers should set out their policies.
This is a very high level overview.
I strongly recommend you read through the gov.uk and ACAS links above and complete the ACAS form then each of you go and talk to your respective HRs who are best placed to advise on your individual circumstances.