how to manage two routers R7000 in one network?

> I have two R7000 in my network but how can I manage both?

   I'll assume that you're talking about wireless access points (WAPs).

      https://community.netgear.com/t5/x/x/m-p/1550066

> For now I can only access the one from which I connected to through
> WIFI.

   "can only" is not a useful problem description.  It does not say what
you did.  It does not say what happened when you did it.  As usual,
showing actual actions with their actual results (error messages, LED
indicators, ...) can be more helpful than vague descriptions or
interpretations.

   You should be able contact the web server on any of these devices by
specifying its LAN IP address in your web-browser address box.  To do
this, you need to know that LAN IP address.  (Names like
"routerlogin.net" don't work, because they depend on using a Netgear
router as the DNS server to talk to that Netgear router, and a WAP is
never the DNS server.)

   When configured as a WAP, the LAN IP address of an R7000 will
normally be different from its default LAN IP address, so "192.168.1.1"
is not a likely candidate.  (This is especially true if you have two of
them.)

   When you set this mode, I'd guess that you were asked to decide how
the R7000-as-WAP was to get its (new) LAN IP address, and were given a
choice between "Get dynamically from existing router" and "Enable fixed
IP settings on this device (not recommended)".

   If you had chosen "Enable fixed IP settings on this device (not
recommended)", then you should know which address you gave it, and you
might now be able to reach it at that address.  (There are complications
to that scheme, too, which is why Netgear says "(not recommended)".)

   Presumably, you chose "Get dynamically from existing router".  That
was fine, and it prevented you from manually selecting bad parameter
values, but it does mean that only the (unspecified) 'Supplier router"
knows which address it gave to each R7000-as-WAP.  And that could change
from time to time.

   Knowing nothing about your (unspecified) 'Supplier router" makes it
hard to give specific advice, but I'd guess that somewhere in the user
interface on that device, there's some kind of report on what Netgear
calls "Attached Devices".  It might be under a name like "DHCP clients".
That's where you should be able to find the IP address which was issued
to each of your R7000-as-WAP devices, and those addresses in a web
browser should get you to the web server on each R7000-as-WAP.

   Once you find it, you might look around in the 'Supplier router"
interface for a way to assign each R7000 a fixed ("reserved") address
(again, something to do with its DHCP server).  Choose some memorable
addresses.  With that done, you would always know which IP address to
use to talk to each R7000-as-WAP.

   For "Enable fixed IP settings on this device (not recommended)", my
usual advice is to shrink the DHCP pool on the main router (if
necessary), and assign a static, non-pool IP address to the access
point, so that it's easy to find the WAP.  For example, DHCP pool: ".2"
- ".199", WAP IP address: ".200" or ".250".  (Something memorable,
outside the pool.  For a second WAP, ".201" or ".251"?)