Spanish charset encoding problem

I am transfering my post from another CMS system and I am having a problem with the charset encoding for the pages. I use the spanish language for my posts. On my previous CMS I used to make one change on the header to charset-latin1 and that will display the correct characters for the spanis languane such as ñ and others like it.

Once I am transfering the posts usintg xml import from an RSS feed.

Where can I change the charset to latin1???

Thanks in advance for your help.