you need to install the Iseries Access client software.
generally this includes a terminal client (greenscreen), the Iseries Navigator, & the ODBC drivers.
If your Iseries account has appropriate permissions you can install the programmer's toolkit.
If you've got an Iseries you are connecting to, you should have someone with qsecofr (security officer) perms who can set you up.
On our Iseries, the Client Access install files are located here:
..oh heck. hold on while I disconnect, vpn, & get that.. 🙂
\\yourservername-or-ip\qBM\ProdData\CA400\Express\Install\Image\