Update index.txt (#12507)

diff --git a/erpnext/docs/user/manual/en/index.txt b/erpnext/docs/user/manual/en/index.txt
index 34bb24e..4019e7d 100644
--- a/erpnext/docs/user/manual/en/index.txt
+++ b/erpnext/docs/user/manual/en/index.txt
@@ -1,6 +1,7 @@
 introduction
 setting-up
 accounts
+asset
 stock
 CRM
 selling