You need 48 Kb mode.

RUN USR 0
LOAD ""

After starting a compiler you see text editor. It's standard Tasword 2.

Important keys:

Text editor's help: Caps Shift + 1
Main menu: Caps Shift + Sym Shift R
Compile: Sym Shift + A

Press Caps Shift + Sym Shift (you see a flashing bottom line), after it
press R (return to main menu). Press L (load text). ZX asks "Are you sure?".
Press Y. ZX asks "File name?". Just press Enter, and you have loaded the
example text, written in COLOSS language.

Press Sym Shift + A (to compile). ZX asks "RUN?". Press Y.

After running the sample, you see short menu "SAVE VERIFY RETURN". Press S
to save machine code of a sample. Press V to verify compiled machine
code to machine code that is saved on tape. And press R to return to
compiler. Now you can try to load and compile other samples (in the same
way).