How can I relate to / interact with allosexuals?
The trick to relating and empathising with others is to recognise that in a way, we are all fundamentally separated from each other. We don't have all the same experiences, or see or think about things in the same way, and we never will. Despite this, we are all human, and each of us is just trying to get by in this world in whatever way we know how. We may not understand exactly why other people feel the way they do, but things like happiness, sadness, fear, etc. are universal.
If you want to support someone else, one thing you can do is just repeat back your understanding of the situation / their emotions and/or ask clarifying questions. Active listening like this is hugely helpful even if it doesn't always seem that way. At the same time, if you don't want/feel up to hearing a vent or giving advice, you are allowed to just say that.