To send mail, you can use the APEX_MAIL package. The following is an example:

Create the page items P2_TOMAIL, P2_FROMMAIL, P2_BODY so that the user can input it. Then create a process as follows:

DECLARE
    l_id NUMBER;
BEGIN
    l_id := APEX_MAIL.SEND(
    p_to                        =>   :p2_tomail,
    p_from                      =>   :p2_frommail,
    p_body                      =>   :p2_body,
    p_body_html                 =>   :p2_bodyhtml,
    p_subj                      =>   :p2_subject,
    p_cc                        =>   :P2_cc,
    p_bcc                       =>   :p2_bcc,
    p_replyto                   =>   :p2_replyto);

FOR c1 IN (SELECT filename, blob_content, mime_type 
FROM your_blob_table
WHERE ID IN (123,456)) LOOP

APEX_MAIL.ADD_ATTACHMENT(
p_mail_id => l_id,
p_attachment => c1.blob_content,
p_filename => c1.filename,
p_mime_type => c1.mime_type);
END LOOP;
COMMIT;
END;

If your mail is not configured, check this link or ask your company DBA to do it.

You can also send the emails from Apex using the database procedure, but this also required the DBA side’s configuration. Check the below link:

Send mail with attachment using UTL_SMTP.