ConnectApi.FeedElementPage fep = ConnectApi.ChatterFeeds.getFeedElementsFromFeed(Network.getNetworkId(), ConnectApi.FeedType.UserProfile, '005R0000000HwMA');
ConnectApi.FeedElementPage fep = ConnectApi.ChatterFeeds.getFeedElementsFromFeed(Network.getNetworkId(), ConnectApi.FeedType.Record, '005R0000000HwMA');
The getFeedElementsFromFeed method is overloaded, which means that the method name has many different signatures. A signature is the name of the method and its parameters in order.
Each signature lets you send different inputs. For example, one signature can specify the community ID, the feed type, and the subject ID. Another signature could have those parameters and an extra parameter to specify the maximum number of comments to return for each feed element.