Information about the DOT app can be found here: https://dinoffentligetransport.dk/nydotapp_en
The app will detect the language settings of your smartphone. We recommend the app if you do not have a Danish travel card (Rejsekort). It is the easiest way of buying tickets where ever you are and whether you want to ride the bus or train. It can be used for all public transportation services by bus or train.
It is also possible to buy SMS tickets on DOT's website. The ticket will be delivered by SMS after payment on the website (available for foreign phone numbers, but please remember to enter the country code). The staff at tourist offices can help you. The SMS ticket website is only available in Danish so you might need a helping hand. SMS tickets are available here: https://dinoffentligetransport.dk/billetkob
If you have a Danish phone number, you can buy a standard SMS ticket via SMS. Read more here: https://dinoffentligetransport.dk/bestil_sms