You can add them, but there will be not data protection in case one of them fails. You have to convert them to dynamic disks in the disk manager before you can merge them.
I would just get 1 tb ssd, keep the OS and etc on the 500gb, and have plenty of room for actual data on the 1tb drive.
This contains complete instructions.
How to combine multiple hard drives into one large volume
It's important to note that you will erase the content of the hard drives participating of the Spanned or Striped volume, as such make sure to backup the data before proceeding.
1. Use the Windows key + X keyboard shortcut to open the Power User menu and select Disk Management.
2. Right-click the hard drive volume and select Delete volume.
3. Click Yes to confirm the deletion of the current volume and all its content.
Repeat steps 2 and 3 on the hard drives you want to combine.
Right-click the unallocated space of the drive and select New Striped Volume (or New Spanned Volume).
4. Click Next.
5. Select the additional disks, one by one, and click Add.
6. Click Next.
7. Leave the default drive letter assignment and click Next.
Make sure the file system is set to NTFS, allocation unit size is set to default, and choose a volume label.
Check the Perform a quick format option.
8. Click Next.
9. Click Finish.
You'll be prompted to convert the hard drive from basic to dynamic, click Yes to complete the task.
WARNING ALL PARTITION will be WIPED.
administrative command prompt
select disk # (whatever it is)