Once you have it set up, it should be fairly easy to set up a subdomain which simply is a reverse proxy to gitea. For instance, this is the nginx config of my gitea instance.
server {
listen 80;
server_name zxq.co www.zxq.co;
root /home/git/gf/public/;
# set max upload to 5 mb
client_max_body_size 5M;
client_body_buffer_size 256K;
location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_max_temp_file_size 0;
proxy_pass http://localhost:3000;
}
listen 443 ssl http2;
# SSL SETTINGS (left out)
}