Welcome here
I suggest to you also what Zozo mentioned, if you need any help, or hint please do not hesitate.
If you want to test only small code, you can do it in 2 ways: The 1st is what mentioned by Zozo, and the sample is very good, it contains a lot of useful stuff. If you do not need any additional allocated memory, then you can create an EXOS 5 header program, it can be loaded directly to the Enterprise, these programs are loaded into 0100h, so you can set a breakpoint to 0100h and the debugger window will appear when the program is loaded.
org 00f0h
db 00,05
dw fillen
db 00,00,00,00,00,00,00,00,00,00,00,00
startpr
(code)
fillen equ $-startpr
The 2nd:
you can load the code directly to EP128emu in debugger window PAGE2, by typing L "file name" 0 xxxx (load address) into top left box, if the code is loaded then with ;xxxx you can give an execution address. ( in this case be aware, if you did not change memory settings, then in most cases at Page 0 first memory segment of EP (in a normal EP128 setup it is 0F8h) ,page 1,2 mostly contains 0ffh segment, which is system segment, and page 3 mostly contains ROM)