Copy everything between -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- (including these delimiters) and paste it in a new text file (usually with the extension .pem or .crt). You can use your favourite (plain) text editor for this, for example Notepad, Gedit, Vim, Emacs (depending on the system you’re using).
Alternatively, you can pipe the output to sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p', as described here:
echo -n | openssl s_client -connect 192.168.1.225:636 | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > ldapserver.pem