The word "settle" can also mean "to become clear". For example, "once the vinegar settled, I saw the sediment on at the bottom of the jar". You can use settle in a similar, figurative way. For example, "the facts settled in my mind and everything became clear to me". Another meaning for "settle" has to do with sinking, falling or drifting down. The sand settled on the bottom. This means it came to rest on the bottom or it sank to the bottom. The word can be used in a figurative way. For example, "he settled into the comfortable chair' or "the frost settled on the ground making everything very slippery". The word "set" can mean to solidify, harden or established. For example, "the glue dried and became set after 10 minutes" or "the jelly I am making for dessert takes about an hour to set. You can use this in a figurative way by saying, "the rules for the game are set. You cannot change them. They are established. They are hard-fast rules". When I SET words in brackets, it means I place them in an established spot. To SET the table means to place the dishes in certain, established place on the table before you eat. These are just a few of the meanings, but I hope they are helpful.

To settle is to set down in one area, supposedly for a while. The sentence: "I'm starting to settle down in my new house." Wouldn't be proper if you said: "I'm starting to set down in my new house." Becuase to set down is more temporary, and is usually used with object. "Just set your backpacks down." "Get yourself settled in a good state of mind." "We're just going to set the foundation."