Hi,
The vested RSU are charged against Income Tax and not Capital Gains Tax, so they should not be declared on the foreign section for capital gains. As the payment is from your employer, the income should be shown in the employment section if it is included in your P60. You would then claim credit for the Tax in the foreign section under 'Employment, self-employment and other income which you paid foreign tax on'.
If it is not included in your P60, please include it in the box on the employment page for 'Tips and other payments not included on your P60'.
You can see that the following guidance advises that when RSUs payout at the market value on what is called ""dividend equivalents"" in either cash or shares, such payments will generally be taxed as earnings in the year they are received.
ERSM20193 - Employment-related securities and options: what are securities: RSUs and dividend equivalents
Thank you.