If a company is offering this facility, you will receive details with other information about the meeting.
Generally, there are two ways of voting. If you receive a paper proxy form, you can go to the named website, usually http://www.sharevote.co.uk and log on using the code number on the proxy form.
If you already have a Shareview portfolio however, the process is even easier. If you have an old style portfolio then just log in and select 'Company Meetings' from the left-hand menu. Details of current meetings where you can send an instruction online will then be displayed. Just click on the highlighted text to confirm your instruction.
If you have a new style portfolio then any company where you can send an instruction will have a 'Vote Now' link shown under the company name on your shares page, simply click this link and use the online form to submit your instruction.