This setting can be configured in the file “httpd-xampp.conf”.

Step 1 – First validate if phpmyadmin is running and accessible locally.
curl http://localhost/phpmyadmin/

Step 2 – Locate httpd-xampp.conf in your Server

root@ip-172-31-20-213:/opt/lampp# cd /opt/lampp
root@ip-172-31-20-213:/opt/lampp# find . -name httpd-xampp.conf
./phpmyadmin/httpd-xampp.conf
./etc/extra/httpd-xampp.conf
Step 3 – Modify httpd-xampp.conf with required permission.

vi ./etc/extra/httpd-xampp.conf

since XAMPP 1.4.3

<Directory "/opt/lampp/phpmyadmin">
AllowOverride AuthConfig Limit
Order deny,allow
Allow from all
Allow from ::1 127.0.0.0/8 0.0.0.0 \
fc00::/7 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 \
fe80::/10 169.254.0.0/16
ErrorDocument 403 /error/XAMPP_FORBIDDEN.html.var
Require all granted
</Directory>