I don’t know where you are, but I’m confident that there will be somewhere to walk near you. If you are in the middle of London, you will struggle to find Lake District views. What is important is that you get outside, spend time walking.
There are so many scientific studies that prove a positive effect from spending time outside. In Japan, they have the term “Forest Bathing” or, as they say, “shinrin-yoku” Spending time taking in the forest atmosphere.
So, you have decided you want to go walking, open your front door, put one foot in front of the other, and walk. Depending on your fitness level, walking to the end of your road might be enough. You don’t want to do too much too fast. Build up slowly. Build up your confidence as you build up your fitness.
Explore your local area. The more you explore, the more you’re going to discover. Now you are going to want to maybe get on the computer or your phone. Find some Ordnance Survey Maps for your area here. Maybe get an OS Explorer paper map for your location.
Now, how to read a map and navigate is a whole massive topic in its own right. For now, though, you can look at it, get to know your area. There are many things on an OS Explorer map. Nature reserves, car parks, museums, etc. Ordnance survey has a 6-page document describing all of them (here). Get to know them, get to know your area, see if you can walk to one of them near you. If you’re not able to get to one of them, maybe you can get to one of them using a footpath ( look on the OS document for Public rights of way).
There are massive amounts of available resources online, in books, courses for learning to read a map. I think everyone should have some basic knowledge of map reading. I think it’s an essential skill.
You do need to remember if you walk somewhere, you will have to retrace your steps back. So if you have been comfortable walking for 1-2 hours, don’t plan a massive trek that will take 4-5 hours. Make sure you have a charged mobile phone and a drink with you. Things like making sure someone knows you are going out for a walk and what time you should be back by are also important.
The best way to know where you can walk is to go for a walk. When you come to a new footpath, go down it. Find some new places, new paths, come back another day, and pick up where you left off.