John, thank you for your reply.
In your initial posting you stated "Already Tried: submitted tax return inc. details of fund and share account summary. I now need to fill in "Capital gains summary"".
By implication it meant you have made a capital gain from maybe sale of investments and that it has to be reported and you wished to know how to fill capital gains summary.
You are now saying that you have the form and that your net dividend was £890. Dividends are reported on the main tax return SA100 under Income Box 3 - dividends from UK companies and these are not reported on any other supplementary pages.
You can download SA100 here
You would use SA108 to report capital gains/losses and not income.
What makes you think you have to complete Capital Gains summary?
I hope this is helpful and answers your question.
If you have any other questions, please ask me before you rate my service – I’ll be happy to respond.