As of this writing (August 2018), Infinity Futures does not officially support the 64-bit version of Sierra Chart. You may find there are DLLs that have not been built for the 64-bit version, and they will break. (All of the DLLs from Forgiving Computers come in both flavors.) However, you can still try it out and see if everything works without causing any problems.
If you want to run the 64-bit version, here is what you need to do.
First, there are two executable files, in the C:\SierraChart\SierraChartTransActMA folder:
The first one is the 32-bit version, the second is the 64-bit version. The 64-bit version is larger than the 32-bit one.
If you want to run the 64-bit version you need close Sierra Chart if not already closed. Then rename the first one to something like sierrachart_32.exe. Then rename the second one to sierrachart.exe. You will then be able to start Sierra through the Infinity application, and it will come up as 64 bit. You can confirm this in Help About.
If you want to switch back to 32-bit rename sierrachart.exe to sierrachart_64.exe and rename sierrachart_32.exe to sierrachart.exe.
You can create two batch files (now called cmd files) to do this. Open notepad and paste the following:
copy sierrachart.exe sierrachart_32.exe
copy sierrachart_64.exe sierrachart.exe
Save the file as Sierra_64.cmd in the C:\SierraChart\SierraChartTransActMA folder.
Repeat with this:
copy sierrachart.exe sierrachart_64.exe
copy sierrachart_32.exe sierrachart.exe
Save it as sierra_32.cmd.
Now when you want to switch to 64 bits, close Sierra run sierra_64.cmd. To switch back run sierra_32.cmd.
Note that when you update Sierra Chart to a new version, it will overwrite both the files, and you will be back on the 32 bit version the next time you open the application. Just switch back to 32 bit before updating, just rename them again. If you forgot to do this, you can rerun the sierra_64.cmd file.