When creating a campaign, you can attach one or more files to it. To do this, at the campaign creation stage, in the "Advanced" tab, click "Add file".
Upload the desired file. Note that you can select only one file at a time.
You can delete a file by clicking on the cross:
ADE, ADP, APK, APPX, APPXBUNDLE, BAT, CAB, CHM, CMD, COM, CPL, DIAGCAB, DIAGCFG, DIAGPACK, DLL, DMG, EX, EX_, EXE, HTA, IMG, INS, ISO, ISP, JAR, JNLP, JS, JSE, LIB, LNK, MDE, MSC, MSI, MSIX, MSIXBUNDLE, MSP, MST, NSH, PIF, PS1, SCR, SCT, SHB, SYS, VB, VBE, VBS, VHD, VXD, WSC, WSF, WSH, XLL.