To adjust the position of dfsle.SignHereTab() from apex tool kit salesforce

​@Burhan 
You can adjust the position of a signHereTab, or any tab by using either the ".withAnchor" method or the ".withPosition" method. 

The withPosition will set the tab using x and y coordinates shown here: https://developers.docusign.com/docs/esign-rest-api/esign101/concepts/tabs/fixed/
The withAnchor will set the tab using anchor strings shown here: https://developers.docusign.com/docs/esign-rest-api/esign101/concepts/tabs/auto-place/

This article shows an example of both under the section "Step 4. Define the recipient tabs"
https://developers.docusign.com/docs/salesforce/how-to/send-envelope-with-tabs/

For example: 

// Create a Text tab
dfsle.Tab myTextTab = new dfsle.TextTab()
.withRequired(true) // Signer must enter value
.withPosition(new dfsle.Tab.Position(
1, // The document to use
1, // Page number on the document
210, // X position
305, // Y position
100, // 100 pixels wide
null)); // Default height

// Create a Sign Here tab
dfsle.Tab mySignHereTab = new dfsle.SignHereTab()
.withScale(1.5) // 1.5 scale
.withRequired(true) // Signing mandatory
.withAnchor(new dfsle.Tab.Anchor(
'signed', // Anchor string
false, // Do not allow white space in anchor string
false, // Anchor string is not case sensitive
'right', // Horizontal alignment in relation to the anchor text
true, // Ignore if the anchor text is not present in the document
true, // Must match the value of the anchor string in its entirety
'pixels', // Unit of the x and y offset properties
20, // X offset
0)); // Y offset