Hi @rmill21 
welcome to the community and great question.
I’ve started doing a weekly round up of what dividends are expected for the week ahead called Cash Taco, it’s probably worth touching in on a Tuesday when I upload that as it’ll be covered.
The £ABF special dividend is 34.3p per share & you need to hold the shares until 16th December at least, this is ex-dividend date. You’ll get the money around 14th January 2022. You don’t need to do anything that else.