is a combination of the conjunction particle から 'from', and the て-from of する. It is used to express when the speaker is making a partially objective opinion about (A). This frequently comes across as 'judging from (A)', or 'based on (A)'. The literal meaning is 'going from (A), (B)'. This simply highlights that (A) is the only information or method available from which an assessment can be made, so 'going from that information, (B) can be said', or 'going with that method, (B) can be said'.からして
will appear directly after the noun which indicates either the method or information from which a judgment will then be made.
Based on his personality, it is probably impossible for me to live with him.
Based on the price, this restaurant must be using fresh ingredients.
Judging from the name, this game seems boring.
is partially objective, this just means that the speaker does not have the full information available to say anything with certainty, and is therefore making a guess about (A) based purely on what appears to be true. Due to this, からして
sentences often have the nuance of 'from the available piece of information about (A), (B) is likely the whole picture'.