Can someone help me understand the basic way a data flow diagram would work with the below use case?

Use Case Name: Gym Member makes or changes a fitness assessment	ID: _1_	Importance Level: High
Primary Actor: Gym Member
Short Description: This describes how a new fitness assessment is made or an existing fitness assessment is changed.
Trigger: Gym Member calls to schedule new fitness assessment or change an existing fitness assessment. Type: External/Temporal
Major Inputs: Description Source Gym Member name Gym Member Desired fitness assessment Gym Member Fitness assessment to change Gym Member Available fitness assessments Calendar file Existing Gym Members Gym Member file	Major Outputs: Description Destination Scheduled fitness assessment Gym Member Scheduled fitness assessment Calendar file Available fitness assessments Gym Member Check Gym Member name Gym Member file
Major Steps Performed Get Gym Member's name. Check Gym Member name with Gym Member file. If new Gym Member, get address and phone number and enter in new Gym Member file entry. If this is a fitness assessment change, find current fitness assessment in fitness assessment file, and cancel it. Get desired fitness assessment time and match with available fitness assessments in Calendar File. When a suitable time is found, enter scheduled fitness assessment in the Calendar file and confirm with Gym Member.	Information for Steps Gym Member name Gym Member File Address Phone number New Gym Member information Fitness assessment to change Existing Fitness assessments Desired fitness assessment Available fitness assessments Scheduled fitness assessments

Use Case Name: Collect new Gym Member information	ID: _2_	Importance Level: High
Primary Actor: New Gym Member
Short Description: This describes how new Gym Member information is collected when a new Gym Member arrives for fitness assessment.
Trigger: New Gym Member arrives for fitness assessment. Type: External/Temporal
Major Inputs: Description Source New Gym Member information Gym Member (Includes name, address, Phone number Injury History Gym Member	Major Outputs: Description Destination Gym Member Information Gym Member file
Major Steps Performed When the Gym Member arrives, determine if he/she has been seen before in this gym. If they have not, have them fill out a Gym Member information form. Use the information on the Gym Member information form to update and complete the Gym Member's entry in the Gym Member file.	Information for Steps Gym Member status Gym Member name Address Phone number Injury history

Use Case Name: Send fitness assessment reminder card and text message	ID: _3_	Importance Level: Medium
Primary Actor: System
Short Description: This describes how reminder cards and text message sent to Gym Members one week prior to fitness assessment.
Trigger: Time to send reminders and text message one week before scheduled fitness assessments. Type: External/Temporal
Major Inputs: Description Source Current date Calendar Scheduled fitness assessments Calendar file Gym Member Contact Info Gym Member file	Major Outputs: Description Destination Fitness assessment notification card Gym Member Text message Gym Member
Major Steps Performed Each day find the fitness assessments in the Calendar file for the day week. 2. Prepare fitness assessment notification card and text message to all Gym Members having fitness assessments.	Information for Steps Current date Scheduled fitness assessments Name Address Fitness assessment Fitness assessment notification card