What happens at a first arraignment for several VOP charges and most recently an arson of a dwelling.

The arraignment is merely the time when you plea guilty or not guilty. If you have hired an attorney then your attorney could enter a written plea. If you can not afford an attorney, the judge will appoint an attorney at the arraignment. Good luck.

At arraignment the State has the opportunity to file formal charges against you and you have the opportunity to enter a plea. For the VOP issues, you can enter an admission or a denial of the affidavit of violation.
It sounds as if there is a new charge as well: arson to dwelling. Often, the VOPs are served up first as the new charge is not ready for arraignment, but they can come at the same time. The same rules apply, with slightly different terminology. For new law violations, an information will be filed and you can plead guilty or not guilty.
Certainly this sounds as though there will be a maximum exposure of prison time and an attorney is called for to represent your interests. If you cannot afford one, one should be appointed.
Though this is not legal advise, it is typical to enter a denial for all VOP issues and a plea of not guilty on any new charges. There needs to be time for your attorney to see the evidence against you, speak with the prosecutor about what they are seeking for any negotiated disposition, and for time to confer with you and for you to think about these issues and your options.

Depending upon the Judge, your VOP charges may track with the new law violation. A plea not guilty would be entered to alow for the discovery process to commence on both the new case and VOP's. Some Judges, however, may accelerate the VOP evidentary hearings. Watch for this, as it is best to resolve the new case first, if at all possible.