Hi Sushrutha,
There are three ways you can do it,

    1. Activate developer mode, open the view you want to edit the label, then click the bug icon on the to panel, then click Edit View : Form/Tree depending on the view you want to modify.Then go to the architecture tab, find your field name in XML and modify it as: 

<field name="field_name" string="Your String here"/>

    2.The next option is to change the string attribute using a custom module you may use the below code for reference:

<xpath expr="//field[@name='field_name']" position="attributes">
    <attribute name="string">Your String Here</attribute>
</xpath>

3. You may override the field as below:

class ModelName(models.Model):
    _inherit = 'model.name'

    field_name = fields.FieldType(string="Your String Here")
​

Hope this answer help you...

Regards

Cybrosys