Can’t edit in Theme

Help! In transfering blog to another server, the original edited files were lost. No, no BU was done. So…have reloaded everything and started from scratch.

Working on editing theme pages — and cannot. At the bottem of the presentation page it says “If this file were writable you could edit it.” where it used to have the update button.

Can anyone help and tell me what happened? Or what I need to do?

Thanks!