Dowload and install the latest Textpattern release available from textpattern.com. Download "lenka.zip", unzip it. Backup your old files before proceeding.
Login to your account using an ftp client and upload the "lenka_img" folder to the "images" directory in your textpattern installation.
If you do not have ftp access, login to your textpattern admin interface and upload the files manually. Then go to presentation > style and change the paths.
Go to admin > plugins in your textpattern admin interface, then install plugins by copying the content of each file in the "plugins" directory into the "Install plugin" field and click "upload". Then scroll down and click "install". Activate the plugin.
Note: Exclude zem_contact_reborn and zem_contact_lang if you don't plan to use the contact form.
Go to presentation > pages in your textpattern admin interface, then replace all pages with the corresponding files found in the "pages" folder. If you want to use the contact form, create a new page.
All files in the "form" directory of the template package correspond to a form with the same name. The second part of the name describes the form type (article, comment, link, misc or file). Go to presentation > forms, then create or replace all appropriate forms.
Go to presentation > styles and replace the default stylesheet with the contents of the "default.txt" file found in the "styles" directory.
Go to presentation > sections and assign pages to your sections.
Go to presentation > pages > contact if you have one and change the attribute "to" of the "zem_contact" tag to your real e-mail address.
Go to presentation > forms > meta and change the "content" attributes of the meta tags.
That's it :)