How to upload a list template
public static SPFile UploadListTemplate(string siteUrl, string templatePath)
{
using (SPSite site = new SPSite(siteUrl))
{
SPDocumentLibrary templates = (SPDocumentLibrary)site.GetCatalog(SPListTemplateType.
ListTemplateCatalog);
System.IO.FileInfo fileInfo = new System.IO.FileInfo(templatePath);
byte[] bytes = System.IO.File.ReadAllBytes(fileInfo.FullName);
return templates.RootFolder.Files.Add(fileInfo.Name, bytes);
}
}