Update accessing.md

docs.it4i/dgx2/accessing.md

-# Before You Access
+# Accessing the DGX-2
+
+## Before You Access
 
 !!! warning
     GPUs are single-user devices. Memories of each GPU are not purged between job runs. Furthermore, they can be read (but not written) by any user at any time. Consider the confidentiality of your running jobs.
 
-# Shell Access
+## Shell Access
 
 The DGX-2 can be accessed by SSH protocol via login node ldgx at the address `ldgx.it4i.cz`.
 
@@ -19,14 +21,14 @@ The DGX-2 can be accessed by SSH protocol via login node ldgx at the address `ld
 [kru0052@ldgx ~]$
 ```
 
-## Authentication
+### Authentication
 
 Authentication is available by private key only.
 
 !!! info
     Should you need access to the DGX-2 machine, request it at support@it4i.cz.
 
-## Data Transfer
+### Data Transfer
 
 Data in and out of the system may be transferred by the SCP protocol.