To create a logic circuit for adding and subtracting two decimal numbers using a full adder and encoder in Multisim, start by utilizing four full adders and two encoders along with a seven-segment display and XOR gates. Users are encouraged to demonstrate their initial approach to the problem to receive more targeted assistance. The discussion emphasizes the importance of showing effort before seeking tutorial help. Participants are looking for guidance on implementing these components effectively in Multisim. Clear instructions and examples would enhance understanding and facilitate the circuit design process.