Hi Adam Heiss, for Mifare DESFire light, after connecting successfully the reader please follow the next steps:
1)First set up an AES 128 key in the key store with 00000000000000000000000000000000 this is the default key, if you have changed the key please put the key value there

2)
1.-select DESFire tab
2.- Activate Idle ( activate card in ISO 14443-3)
3.-RATS-PPS ( Activate card in ISO 14443-4)
4.-go to SELECT
5.-select by DF name
6.-verify this DFname ( usually is already set up)
7.- send ISO select command

2)
8.- go to authentication
9.- select card key 03 ( as you can see in the DS the key 03 is the one with R/W rights to file 00) so if you want to write to different files please check the file settings before to know which key is used for R or W or R/W
10.- select the Key from keystore that has the value either the default value inc ase you have not changed or the changed one
11.-send Authenticate EV2 first
12.-send Authenticate EV2 non first

3)
13.- go to Data file Access
14.- select ID 00
15.-select fully enciphered communication
16.-offset to 00
17.-length 0x20 ( in this case I will write 32 byte)
18.-write the 32 bytes
19.-Write Data
20.-just to confirm please read the data 
Please follow this and let me know if this worked.
Have a great day !
BR
Jonathan