It is not possible* to hide Tor usage from websites you visit. Tor publishes the list of exit nodes and provides a tool to detect if traffic comes from the Tor network (see here as to why). Website owners can therefore choose to block some or all Tor users, if they wish.
*It is possible to configure a VPN over Tor (not Tor Browser) - in which case traffic will appear to have originated from the VPN’s IP address. However, as well as further degrading connection speed, anonymity is also compromised - i.e. it is only as good as the anonymity gained from your VPN provider, which may be nil. You also won’t be able to visit .onion addresses.
If you just need to read websites which block Tor (& not login or otherwise post data) you can archive the webpage & then read the archived page. I do this a lot and although time consuming it does circumvent a Tor block for my ‘read-only’ needs. Try archive.org or archive.is (http://archiveiya74codqgiixo33q62qlrqtkgmcitqx5u2oeqnmn5bpcbiyd.onion/). The former is slow & you may need to cycle through a few exit nodes if you are rate-limited. The latter requires you to complete a CAPTCHA.