SLA definitions can be created under Time to SLA Menu > SLA Configuration.

TTS SLAs are based on JIRA workflows. 
After selecting JIRA Workflow, click on Add New SLA Definition button. 

 

SLA definition form will be displayed as below.

The toggle button changes the state of the SLA as either Active or Frozen. SLA data will not be calculated for this SLA until it is re-activated. SLA data of uncompleted issues will be lost after the first transaction in the issue. Frozen SLAs will be shown grayscaled in the SLA list.


Please bear in mind that SLA End Date is not the 'negotiation date', it is the 'actual end date' of the issue. 
Selected date custom fields, statuses and comment will determine the actual start/end date of the SLA. 


Start/End SLA custom field support is available since TTS 5.10.0 for JIRA 6.3 - 6.4.12 or TTS 6.5.0 for JIRA 7.x


Start/End SLA comment support is available since TTS 7.0.0 for JIRA 7.x

What is the difference between SLA Start/End and SLA Deadline Fields?  
Even though they seem to be similar, they are not. 

There is no limit on the count of defined SLAs. All SLAs are grouped by workflow selection.

Besides the cog icon, there are some icons/lozenges which indicate whether there is an additional configuration for SLA. 

 means there is additional JQL defined for this SLA.

means there is/are paused status(es) for this SLA.  

 means there is/are reset field(s) for this SLA. 

              means there is notifier for this SLA.

 

By clicking cog icon, SLA definition can be edited, deleted, cloned, moved to another workflow, etc.

Also, there are handy settings like, Pause SLA, Reset SLA , and SLA Notifier which are described below

Pause SLA (Set Pause Conditions for TTS 9.0.0+)  link displays a dialog in which SLA can be configured to have paused staus(es). If the issue reaches to one of these selected "Paused Statuses" the timers will immediately stop to count for SLA. 

Reset SLA (Set Reset Conditions for TTS 9.0.0+)  link displays a dialog seen below. When at least one of the selected fields of the issue changes, the SLA timer resets immediately. 

Move SLA option changes the corresponding workflow of the SLA definition. It is accessible through change workflow link in the cog icon in SLA definition page.