if you are using nginx, i suggest you download the file from https://www.phpmyadmin.net/downloads/ and extract it anywhere you want.
after that just make a configuration on your nginx (the default is /etc/nginx/sites-enable/default), something like:
server {
        listen   80; ## listen for ipv4
        server_name  phpmyadmin.x; ##change it as you wish
        root   /var/www/sites/phpmyadmin; ##path to your phpmyadmin directory
        index  index.php;
    location ~ \.php$ {
                try_files $uri =404;
                fastcgi_pass unix:/var/run/php5-fpm.sock; ##just adjust with php7 version
                fastcgi_index  index.php;
                fastcgi_param  SCRIPT_FILENAME  /var/www$fastcgi_script_name;
                include         fastcgi_params;
        fastcgi_read_timeout 300;
        }
        # deny access to .htaccess files, if Apache's document root
        # concurs with nginx's one
        #
        location ~ /\.ht {
                deny  all;
        }
}
then edit your /etc/hosts and add phpmyadmin.x (change it if you want) on 127.0.0.1
restart your nginx. (service nginx restart)
make sure you already install php7 lib for mysql. maybe php7-mysql or something like that. and then restart the php-fpm