It is very easy to integrate Xcart with Nelichso. Please find here with the steps you can follow to integrate it.
1) Connect your zencart website through FTP
2) Go to the folder skins/default/en/header
3) Download the file meta.tpl
4) Login to your nelichso account.
5) Click on menu " HTML Code " from left panel.
6) Select the type of code you want to use.
7) Paste it anywher in meta.tpl.
8) Uplod the file html_header.php to your website through FTP
That is it. You are done.