Try this
Component:
<aura:component >
<aura:attribute name="text" type="String" default="Enter your name here.."/>
<div style="position:relative;" class="slds-size_1-of-4">
<lightning:input type="text" label="Name" name="nameInput"/>
<lightning:helptext content="{!v.text}" iconName="utility:info" class="popover"/>
</div>
</aura:component>
Style:
.THIS {
}
.THIS .popover {
position: absolute;
left: 14%;
bottom: 65%;
}
You can add your own style to align the helptext component wherever you want.