Using an app is the easiest. That is country specific as is the Divine office. You dont say which country you are in so I can’t recommend one but I think the first poster is American so you can take their advice if you are too.
If you want to buy a book then make sure you get one suitable for your country for instance, America and England do not use the same book. The book comes in many volumes but if you were only doing say Morning, Evening and Night, you could get these all in one book and would not need to have all the volumes. I do those 3 which are the main and taught myself to use the book with relative ease. The front of the book has a lot of information which is reasonably easy to follow. I am in an Order though so was able to view other people using the book and follow along with them before buying my own book. I also practiced on the app for a year or so first, you should not have to buy the app, or at least in UK you dont, though you can. Our parish website has the app/website link on it so all are encouraged to pray it, in fact most parishes have the link. Once you understand about the church calendar it is not to hard to get the hang of and it is not to serious if you go wrong, googling it can be helpful. I use the app to say Office of readings. My book has day prayers as well so it is well worth it’s money, though it was costly (about £30) that is not a lot for others though it is for me. I recommend Night prayer too, but I agree Morning and Evening are the two usual for us lay people though they take only about 15 mins or so each. There are 7 in total though how many you pray is up to you, you can vary it as you wish, but the 2 or 3 are usual. You can always start with one and move to 2 when you are ready. God bless you