Not very clear on your question. Here is a thought though -
You can create an email alert to use the template you have created. Then create a workflow on the custom object to send and email and associate the email alert to the workflow.
Since you have posted this question under Force.com sites, I am assuming you want to send an email alert, that's triggered by a workflow due an an action happening on the site. Is that right?
Can you please elaborate what exactly you want to do?
I am having Email template. i need to use that template while clicking "send email" custom button. means, when user clicks that button,email has to send with the "email template".
Not very clear on your question. Here is a thought though -
You can create an email alert to use the template you have created. Then create a workflow on the custom object to send and email and associate the email alert to the workflow.
Since you have posted this question under Force.com sites, I am assuming you want to send an email alert, that's triggered by a workflow due an an action happening on the site. Is that right?
Can you please elaborate what exactly you want to do?
I am having Email template. i need to use that template while clicking "send email" custom button. means, when user clicks that button,email has to send with the "email template".