You can load and run XYBASIC for the IMSAI 8080 with SIO set for 9600b, assuming you have a ROM monitor can can accept binary HEX files or you have toggled in the bootstrap loader into RAM first. Also assuming you have a PC running a terminal program such as TeraTerm on the other end:
1. Prepare your PC terminal to transmit with a 10ms delay, 8N1.
2. Prepare the IMSAI to receive a HEX file. For most ROM monitor programs, the command L (load tape) should work.
3. From your PC terminal program send xybasic.hex as a binary file.
4. You should see the binary file contents stream line by line as the file downloads into your IMSAI from the PC. The 10ms delay is necessary (or more depending on your RAM) to allow your IMSAI to keep up with the incoming data stream without error.
5. It will take a while. The file is 39K. Obviously you'll need enough RAM in your IMSAI, but the actual BASIC does not take up all of this space. It may be possible to trim your hex file, not sure.
6. When the download completes, stop your IMSAI and examine address 0000. It may be necessary to set your terminal to 7N1, but try 8N1 first, RUN from 0000
If all goes well you'll be greeted by the screen above.
Here's the manual